Chapter 8: Examination of Function

Aclinician needs to consider the purposes of obtaining the measurement in deciding which measure of function to use. For example, is the measure to describe a specific activity limitation or describe an individual's overall level of function? Will the measure be used to assess outcomes of an episode of care, determine the destination at discharge, obtain reimbursement, meet regulatory requirements, or a combination of all of the above? As function may incorporate performance at the level of body systems, the person, and society, or a combination of these, and the clinician should be cognizant of the ability of the measure to capture the appropriate information.

The ultimate objective of any rehabilitation program is to return the individual to a lifestyle that is as close to the premorbid level of function as possible or, alternatively, to maximize the current potential for function and maintain it. For an otherwise healthy person with a fractured arm, this may be a reasonably simple process: improving range of motion, strength, and impairments in body function will reestablish skills in the performance of activities, such as dressing and feeding. However, considering the person with a stroke as an example, the task is much more complex because the problems are much more extensive, complicated, and interwoven. The two cases, however, are broadly similar. In both instances, the therapist begins by describing the problem in functional terms obtained from the history, performing a systems review and detailed examination using selected tests and measures, evaluating the data, establishing a diagnosis and prognosis, implementing interventions to reduce or to eliminate the problems identified, and documenting the progress toward the desired functional outcome.¹

Every individual values the ability to live independently. The construct of function encompasses all those tasks, activities, and roles that identify a person as an independent adult or as a child progressing toward adult independence. These activities require the integration of both cognitive and affective abilities with motor skills. Functional activity is a patient-referenced concept and is dependent on what the individual self-identifies as essential to support physical and psychological well-being, as well as to create a personal sense of meaningful living. Function is not totally individualistic, however; there are certain categories of activities that are common to everyone. Eating, sleeping, elimination, and hygiene are major components of survival and protection common to all animals. Particular to humans are the evolutionary advancements of bipedal locomotion and complex hand activities, which permit independence in the personal environment. Work and recreation are functional activities in a social context.

This chapter presents a conceptual framework for examining functional status based on the International Classification of Functioning, Disability, and Health (ICF) and introduces the reader to terminology used in the field (see also Chapter 1). It presents an overview of the purposes of the examination of function and the range and rigor of formal test instruments currently available to clinicians and researchers. Considerations in test selection and principles of administration are also presented.

Chronically ill and disabled persons represent a large segment of the population in the United States. In 2008, approximately 37 million Americans (12%) were considered to have a disability (limited in their usual activities due to one or more chronic health conditions).² Traditionally, these individuals have been categorized or classified according to their medical diseases or conditions. Medical procedures such as physical examination and laboratory tests are the primary tools to delineate the problems created by disease. Strict focus on a biomedical model, with its emphasis on the characteristics of disease (etiology, pathology, and clinical manifestations), may contribute to reducing patients to the medical labeling of these individuals; for example, referring to people as amputees, paraplegics, or arthritics rather than as individuals with these conditions. This model virtually ignores the equally important psychological, social, and behavioral dimensions of the illness, which accompanies the disease. Illness refers to the personal behaviors that emerge when the reality of having a disease is internalized and experienced by an individual. Factors related to illness often play a key role in determining the success or failure of rehabilitation efforts well beyond the nature of the medical condition that prompted a patient's referral to physical therapy. In helping the individual with a disease, physical therapists come to understand each person's illness as well.

A broad conceptual framework is necessary to fully understand the concept of health and its relationship to function and disability. Terms such as well-being, health-related quality of life, and functional status are often used interchangeably to describe health status. The most global definition of health has been provided by the World Health Organization (WHO), which defined health as "a state of complete physical, mental, and social well-being, and not merely the absence of diseases and infirmity."^{3, p. 459} Although such global definitions are useful as philosophical statements, they lack the precision necessary for a clinician or researcher.

In order to describe the components of health and provide a unified and standard language and framework for the description of health and health-related states, the International Classification of Functioning, Disability, and Health (ICF) was developed.⁴ The ICF was endorsed by the World Health Assembly on May 22, 2001, for international use and complements other classifications of the WHO such as the International Classification of Diseases, 10th revision (ICD-10).⁵ Whereas the ICD-10 is a classification of diseases, disorders, and other health conditions, the ICF attempts to provide a meaningful description of the components of health and its relationship to a person with the health condition. Since its development the use of the ICF has been endorsed by the physical therapy community, including the World Confederation of Physical Therapy (WCPT) and the American Physical Therapy Association (APTA), and is gradually replacing other frameworks.⁶ Table 8.1 presents an overview of some of these other frameworks, including of the ICF's predecessor, the WHO's International Classification of Impairments, Disability and Handicaps (ICIDH)⁷ and the Nagi model⁸ on which the process of disablement in APTA's Guide to Physical Therapist Practice¹ is based.

Function in the ICF is an umbrella term encompassing all body functions and structures, activities, and participation, whereas disability is a term that encompasses impairments in body functions and structures, activity limitations, and participation restrictions. Both function and disability are represented in the ICF, in contrast to previous frameworks, to provide for the description of a continuum of the components of health from positive aspects to items an individual is not able to perform or perform in a limited manner or with assistance.

The ICF framework consists of two parts. The first part describes components of function and disability in the context of health, whereas the second part describes contextual factors which may interact with the components of the first part (Fig. 8.1). These components of the ICF do not model a process of disablement, such as in previous frameworks; rather, the ICF provides an approach to classification of function and disability from multiple perspectives. The relationship between components and parts of the ICF does not imply causality. Bidirectional arrows are used in Figure 8.1 to represent a complex relationship. For example, a health condition such as angina may influence aspects of mobility such as gait, whereas at the same time increasing one's mobility by performing a regular walking program may influence the management of the health condition. In addition, a limitation in one component of the framework does not imply limitations in other components.

Body functions are defined by the ICF as the physiological functions of body systems, and body structures are parts of the body such as organs, limbs, and their components. Impairment is the term used to refer to problems in body function or structure. Although two separate sections are used to classify body functions and structures in the ICF, the classifications are designed to be used together. For example, the chapter titled "Neuromuscular and Movement-related Functions" in the body functions classification correlates with the chapter titled "Structures Related to Movement" in the body structures classification. Hence, for a person with rheumatoid arthritis a clinician may use aspects of the body functions classification to describe range of motion of the interphalangeal joints and muscle performance of the hand intrinsic muscles and the body structures classification to describe the integrity of the joints of the hand. The headings for the chapters in the ICF classification of body functions and structures are in Table 8.2.

The ICF defines activity as the execution of a task or action by an individual and participation as involvement in a life situation. The terms used to describe problems in these domains are activity limitations and participation restrictions. Through the definitions of activity and participation an attempt is made to differentiate what a person can do because of characteristics of the individual and those of society. In the ICF, however, a single list covers both activity and participation. In contrast, a draft of the ICF, the ICIDH-2, used separate lists to distinguish activity from participation.⁹ Instead of separate lists, the ICF allows users to operationally differentiate activities and participation. Possibilities suggested in the ICF include (a) designating some domains as activities and others as participation with no overlap, (b) designating some domains as activities and others as participation allowing for overlap, (c) designating all detailed domains as activities and the broad categories as participation, and (d) using all domains as both activities and participation.^{4, pp. 234-237} To date, no standard exists for the distinction of the classification of activity and participation, and physical therapists should be aware of the potential uses of the classification for practice and research.¹⁰

The headings for the nine chapters in the ICF classification of activities and participation and examples of classification within a chapter are presented in Figure 8.2. The chapters are considered the first-level of classification and can be used to categorize positive and negative aspects of function. The second-level of classification includes categories of different actions, tasks, and activities. Subcategories provide additional detail for the main categories. For example, moving around is a category within the mobility domain of the ICF, and crawling is a subcategory of the moving around category.

The second part of the ICF is labeled "contextual factors," which represent the complete background of an individual's life and are included to represent factors that may interact as facilitators or barriers to the components of function. The contextual factors are considered as either barriers or facilitators to function from the perspective of the individual whose situation is being described. Contextual factors have two components: environmental factors, which are external to the individual and can have positive or negative influence on performance, and personal factors, which are features of the individual such as age, gender, and race that are not part of a health condition or health state. Due to the bidirectional nature of the ICF framework contextual factors may also be modified by the components of part 1. Environmental factors are classified by the ICF; however, a classification of personal factors is notably omitted (Table 8.3).

The ICF, and models such as the Institute of Medicine's enabling-disabling process (Fig. 8.3),¹ emphasize the interaction between the person and the environment as critical to understanding functioning and disability.

Physical therapists can help change discriminatory social attitudes and environmental restrictions such as architectural barriers that stigmatize individuals and restrict participation in all aspects of society. The modification of factors that are barriers and incorporation of factors that are facilitators is as important to functioning as the amelioration of activity limitations.¹¹

In addition to providing a framework for the classification of function, the ICF provides a classification scheme for coding, which, although not yet in widespread use by physical therapists, may be particularly intriguing in its delineation of actions, tasks, and activities in an implicit hierarchy of functioning. Within this hierarchy, actions (e.g., rolling, bending, sitting, standing, lifting, and reaching) are constituents of tasks and activities (e.g., bathing, dressing, and grooming). Tests and measures of actions are particularly relevant to physical therapist practice as they capture the complex integration of systems that permits an individual to maintain a posture, transition to other postures, or sustain safe and efficient movement.

Although typical patterns of deficits in body functions and problems in activities may typically exist in certain disease categories, the exact empirical relationship between a particular set of impairments in body functions and structure and activity limitations is not yet known.¹² The cause-and-effect relationship between an impairment and an activity limitation is most often inferred in the clinic from empirical evidence. For example, physical therapists may assume that the reason a patient cannot transfer independently is causally linked to the fact that the individual has lost enough lower extremity range of motion at the hip (e.g., hip flexion contractures) to prevent balancing in a fully upright posture. The return of activity following remediation of the impairment of joint mobility is then considered clinical evidence of a relationship between the impairment and the limitation. For data to be clinically useful, assessment of a patient's function by a physical therapist must include all of the appropriate components.

Purpose of Examination of Function

Analysis of function focuses on the identification of pertinent activities and measurement of an individual's ability to successfully engage in them. In essence, functional testing measures how a person does certain tasks or fulfills certain roles in the various dimensions of living described in the framework of the ICF. Application of selected functional tests and measures yield data that can be used as (1) baseline information for setting function-oriented goals and outcomes of intervention; (2) indicators of a patient's initial abilities and progression toward more complex functional levels; (3) criteria for placement decisions, for example, the need for inpatient rehabilitation, extended care, or community services; (4) manifestations of an individual's level of safety in performing a particular task and the risk of injury with continued performance; and (5) evidence of the effectiveness of a specific intervention (medical, surgical, or rehabilitative) on function.

General Considerations

Physical therapists possess a unique body of knowledge related to the identification, remediation, and prevention of movement dysfunction. Thus, they have traditionally been involved in the examination of physical function. Other members of the rehabilitation team, including the occupational therapist, nurse, rehabilitation counselor, and recreational therapist, are also typically involved in administering and interpreting functional tests. Some formal instruments were designed to be completed collectively by the team. Other tests are compiled in separate sections by specific health professionals and housed together in the patient's chart. Where teams exist, physical therapists are typically responsible for the testing of aspects of function related to mobility, such as bed mobility, transfers, and locomotion (wheelchair mobility, ambulation, negotiation of stairs and graded elevations, walking for longer distances in the community, and so forth). Instruments to measure activities of daily living (ADL) may be administered by a physical therapist alone or cooperatively with other health professionals. When overlap among team members exists, for example, the performance of toilet transfers, the data may be collected by the physical therapist, an occupational therapist, or a nurse. In these instances, testing should be coordinated to reduce duplication and unnecessary patient stress. In noninstitutional settings or where there is no team, the physical therapist is often responsible for determining all aspects of these instruments.

Testing Perspectives

Function tests can utilize two highly divergent perspectives on what is to be tested or measured by the physical therapist. It is extremely important that the therapist determine in advance whether data are needed to describe the habitual level of a patient's ability to do certain tasks and activities, or to identify the patient's capacity to perform certain tasks and activities, whether the patient habitually performs up to that level or not, or even performs them at all. These perspectives are incorporated within the ICF by the constructs of performance and capacity and the ICF allows for the separate coding of both constructs.

These divergent viewpoints directly affect what types of tests and measures should be chosen and what parameters of measurement are appropriate to yield data useful to making clinical judgments. Most important, physical therapists must consider the differences between capacity for function and habitual function in determining the prognosis for rehabilitation and estimating the likelihood of the success of an intervention. Patients accept a therapist's recommendations regarding the anticipated goals of treatment only if there is the perceived need and motivation to function habitually at the highest level of ability. Understanding the difference between what a person actually does or would be willing to do and what that person potentially could do is an essential component of designing realistic, and achievable, functional goals. For example, even though a person might have the capacity to climb stairs, there may not be any willingness to do so. Ultimately, physical therapists must abide by each patient's own decision regarding which tasks and activities will be incorporated into a daily routine and what is a meaningful level of function, regardless of the therapist's professional opinion.

Irrespective of the particular instrument used, there are several basic considerations to be kept in mind. The setting chosen must be conducive to the type of testing and free of distractions. Instructions should be precise and unambiguous. Testing may be biased by fatigue. If a patient performs best in the morning but tires by afternoon, an accurate determination of functional ability must consider the variation in the patient's performance. Therapists should be aware of patients whose energy fluctuates during the day, and interpret the data accordingly. In general, information related to body functions and body structure, activities, and participation, as well as personal and environmental factors, should be generated during the initial examination (or as soon as feasible) so the information may be considered together to develop a picture of a patient's function. Retesting should occur at regular intervals during treatment to document progress and before discharge from the episode of care.

Types of Instruments

Performance-Based Tests

A performance-based test involves observing the patient during the performance of an activity. Generally speaking, the therapist who chooses a performance-based test is searching for an indication of what a patient can do under a specific set of circumstances, which may or may not be similar to the natural environment in which the patient functions. If a performance-based test is chosen with the intention of making inferences about how the patient will perform at home, the conditions and setting should be as similar as possible to the actual environment in which the patient usually performs the tasks and activities. A performance-based approach may be used either to describe the patient's current level of function or to identify the maximum level of function possible.

During the administration of the test, each task is presented and the patient is asked to perform it. For example, to examine current level of function in wheelchair mobility, a patient would receive this instruction: "Push your wheelchair over to that red chair and stop." To determine the patient's maximum level of function in this activity, the instruction might specify a particular manner of performance: "Push your wheelchair over to that red chair as quickly as you can and stop." Understanding the difference between these two commands, even though both are observation-based performance of wheelchair mobility, is essential to sound clinical decision making. Data from the first example identify only what the patient can do under specific circumstances, but does not support the inference that the patient will be able to wheel across a busy intersection in the short time span allotted to a typical pedestrian walkway. The form of the instruction determines whether an inference can be made about the patient's maximal level of function in formulating the goals for intervention and the plan of care.

In either case, a patient is given no additional instructions or assistance unless he or she is unable or unsure of how to perform. Then only as much direction or assistance as is needed is given. Appropriate safety precautions should be taken during the session so that the patient does not attempt tasks that are potentially dangerous.

A number of tests of impairments are sometimes also referred to as functional performance measures, including the 6-Minute Walk Test,¹³ the Physical Performance and Mobility Examination,¹⁴ the Functional Reach Test,^15,16 the Get Up and Go Test,¹⁷ the Timed Up and Go Test,¹⁸ and the Physical Performance Battery.¹⁹ A performance instrument of this sort typically measures either a complex integration of impairments, the performance of actions, or a combination of both by direct observation. Overall, the tests do provide some insight into the individual's capabilities to maintain a posture, transition to other postures, or sustain safe and efficient movement. The data from such a test, gathered under controlled conditions, characterize a person's performance limitations as a result of impairments, and may purport to predict the success or failure of an individual in performing goal-directed tasks or activities under natural conditions, using a score that summates the combined effects of impairments throughout and across systems on movement dysfunction. Each of these tests can contribute to an understanding of an aspect of a person's function, but they should not be used to represent all aspects of function. Although these tests employ the method of direct observation of performance, they most often do not measure the task or activity as it might be accomplished in the "real" world of the patient, which is also influenced by motivation and habit.

Self-Reports

In contrast to the method of direct observation, useful data on how a person functions may also be gathered by self-report, in which the patient is asked directly either by the therapist or a trained interviewer (interviewer report) or through the use of a self-administered report instrument. The critical issue in the ability of a self-report to capture function correctly and completely lies in providing clearly worded questions without language bias, concise directions on completing the questions, and a format that encourages accurate reporting of answers to all questions. Self-report is a valid method of determining function and may be preferable to performance-based methods in some circumstances.²⁰ Self-reports should be designed so that questions are asked in a standard format and answers are recorded as specified by the predetermined choices. Long paper-and-pencil tests may be difficult for those with upper extremity disability.

Clinical personnel who will act as interviewers must be trained to administer a questionnaire. Interviewers should practice until they have reached a high degree of agreement with expert examiners of the same cases. Periodic retraining may be necessary if interviewers do not have frequent practice administering the instrument. The interview should be scheduled with the patient in advance and conducted in an environment conducive to complete concentration. Interviews may be conducted by phone or in person, but the mode of administration should be kept consistent if comparisons of the data are to be made. Ad lib prompting by the interviewer or caregivers for answers is discouraged because these intrusions into the patient's self-report tend to bias results. If the patient has had help in filling out a form or responding to questions, this should be noted. Similarly, if the data have been provided by a spouse, family member, or caregiver, this should be documented as well.

The distinction in perspectives on function that was discussed regarding performance-based measures of function also holds for self-reports. It is extremely important to distinguish between questions that indicate a person's habitual performance (e.g., "Do you cook your own meals?") and those that identify a person's perceived capacity to perform a task (e.g., "If you had to, could you cook your own meals?"). It may also be important to distinguish between an individual's performance of an activity and his or her confidence in performance of an activity. For example, confidence and performance for 21 items are measured in separate scales in APTA's Outpatient Physical Therapy Improvement in Movement Assessment Log (OPTIMAL).²¹

The time frame reference of self-reporting is also a relevant consideration. A therapist should decide in advance if the relevant "window" on a person's functional level is the past 24 hours, last week, last month, or the previous year. One can easily imagine how the same person might respond differently regarding the same functional activity depending on frame of reference. Instruments that examine only short-term objectives may not relate well to the long-term objectives of a rehabilitation program.

Instrument Parameters and Formats

Performance-based and self-report instruments grade performance on a number of different criteria in a variety of formats. There is no one parameter or format that is perfect for every type of clinical encounter or research need. It is particularly important that documentation of a patient's progress not be blunted by floor or ceiling effects. For example, if a therapist wishes to measure changes in function among generally well elderly patients and the most advanced functional activity on an instrument measures "independent ambulation on level surfaces," there would be no room to demonstrate either progression or decline except around ambulation on level surfaces. Similarly, a patient who was severely debilitated might improve in transfers from needing the maximum assistance of two persons to maximum assistance of one. If the instrument only measures change from "maximum assistance" to "moderate assistance," this patient's real improvement will not be recorded.

Descriptive Parameters

Therapists should use descriptive terms that are well defined and unambiguous. Meanings of descriptive terms should be clear to all others using the medical record. Box 8.1 provides a sample set of acceptable terms and definitions. Additional terms used to qualify function include dependence and difficulty. Most often, the term independent refers to the complete absence of a need for human or mechanical assistance to accomplish a task, but some scoring systems consider reliance on devices and aids as a modified form of independence when used without the help of another person. The use of equipment during the performance of a functional task should be explicitly noted; for example, "independent in ambulation with axillary crutches" or "independent in dressing with adapted clothing and a long-handled shoe horn."

Difficulty is a hybrid term that suggests an activity poses an extra burden for the patient, regardless of dependence level. It is unclear whether it is a measure of overall perceptual-motor skill, coordination, endurance, efficiency, or a combination of measures. Difficulty can be measured in two ways. One approach assumes that difficulty is likely to be present and quantifies the degree of difficulty that the individual experiences while performing the activity (e.g., "How much difficulty do you have while doing household chores? None, some, or a great deal?"). The other approach quantifies the frequency that the difficulty is encountered (e.g., "How often do you have difficulty putting on your shoes? Never, sometimes, very often, or always?").

Often it is helpful to qualify a person's performance by linking observations with nonspecific indicators of impairments such as the energy consumption required to complete the functional task and the degree to which patients must exert themselves to engage in the activity. Simple measurements of a patient's physiological response to activity generally include heart rate, respiratory rate, and blood pressure, obtained at rest (baseline measurements), during (as possible), or immediately after completion of the most stressful elements of the activity. For example, "heart rate increased to 100 beats per minute with independent ambulation on stairs; no increase in respiratory rate." In addition, the patient's perceived fatigue, perception of exertion, and overt signs of physiological stress, such as shortness of breath, also should be noted. These notations may assist the therapist in a quick identification of some obvious impairments that limit function, which should be followed by more specific tests and measures of impairment.

Additional descriptors frequently used to qualify functional performance further include (1) pain, (2) fluctuations according to the time of day, (3) medication level, and (4) environmental influences. Any factors that modify a patient's function should be carefully noted and considered by the physical therapist evaluating examination data.

Quantitative Parameters

The time it takes to complete a series of activities is often used to enhance a therapist's quantification of function when a given speed of performance is required or an improvement in performance speed is expected. A common example of timed functional skills is found in premedication and postmedication performance of individuals with Parkinson disease who are placed on l-dopa therapy. Examples of activities that may be timed include (1) walking a set distance; (2) writing one's signature; (3) donning an article of clothing; and (4) crossing a street during the time of a "Walk" light. Scores of timed tests should not be taken as absolute, but rather as one dimension of performance. Although the ability to complete a particular activity in a specified period of time does provide one kind of important data on a patient's overall ability, it may not always be correct to conclude that what is being measured as "quicker" can be interpreted as "better." For example, the patient may get dressed quickly (within seconds), but do so with poorly coordinated movements and a haphazard outcome. When the task is slowed down, the movements may become more coordinated, with a more satisfactory functional outcome, even though the time taken to do the task increases. Similarly, certain medical conditions that affect energy expenditure may require that the patient properly pace a functional activity to complete it successfully. Thus, time scores alone do not always yield the complete functional picture. When interpreted in light of other aspects of the patient's clinical presentation, they do provide an added dimension to the evaluation of data collected during a functional examination.

Response Formats

Function can be measured with tests that report data as nominal, ordinal, interval, and ratio measures. The clinician should consider the uses of the measure when deciding which format to use. In cases where the clinical decision is nominal, such as is the patient ready for discharged to home, a nominal measure such as whether the patient can independently ascend 10 stairs may be adequate. When ratio measures are obtained, such as the score on a Berg Balance scale, the clinician may interpret the score as a dichotomous measure related to the decision (e.g., Does the patient have or not have adequate balance for discharge to home?). In cases where the clinical decision is more complex, such as the amount of assistance a patient needs with activities, nominal measures cannot be used and the measure should reflect the type and amount of information needed for the decision.

Nominal Measures

One of the simplest formats in functional tests uses a nominal level of measurement by presenting a checklist of various functional tasks on which the patient is simply scored as able to do/not able to do, independent/dependent, completed/incomplete, or the like. The results are not particularly descriptive of the exact nature of an individual's limitations and usually require further examination before interpretation. Nominal measures, however, may be helpful in making dichotomous decisions. For example, knowledge of the ability to perform ADL skills by themselves is important in deciding if a patient can be discharged, or not, to living independently at home.

Ordinal Measures

A few tests use descriptive scales that describe a range of performance or the degree to which a person can perform the task. Most commonly, the scales are ordinal or rank-order scales (e.g., "no difficulty," "some difficulty," or "unable to do"; or "always," "sometimes," "rarely," or "never"). Scales may be graded in ascending or descending order. The primary drawback in using such a system to score function is that these grades do not define categories that are separated by equal intervals. For example, it is not possible to tell whether the patient who went from maximal assistance to moderate assistance changed as much as a patient who also went one level between moderate assistance and minimal assistance.

Interval Measures

Summary or additive measures grade a specific series of skills, award points for part or full performance, and sum the subscores as a proportion of the total possible points, such as 60/100 or 6/24 and so forth. Although the scales typically may include a score of zero, this value represents a floor effect of the scale and not necessarily the absence of the construct. One example of a summary measure, which is well known to physical therapists, is the Barthel Index.²²

Some formal, standardized instruments for testing function summarize detailed information about a complex area of function into an overall index score. Use of these instruments facilitates the interpretation of complex data and enables the clinician to perform crossdisease, cross-program, and cross-population comparisons of function. Caution must be exercised in considering only summated scores, however, because potentially important individual differences in functional ability can be masked.²³ A patient who is limited in only a few of the many tasks covered on a functional test will most likely score well, despite what could be substantial limitations in discrete functional activities that are pertinent to the physical therapist's anticipated goals of treatment. Similarly, two patients with the same numeric score might be quite different in their functional deficits, having gained (or lost) their points on different activities. Although these measures yield a "hard number," which is regarded statistically as an interval level of measurement, the degree to which "points" are truly equal intervals or only ordinal should be carefully scrutinized.

Ratio Measures

Visual or linear analog scales attempt to represent measurement quantities in terms of a straight line placed horizontally or vertically on paper (Fig. 8.4). The endpoints of the line are labeled with descriptive or numeric terms to anchor the extremes of the scale and provide a frame of reference for any point in the continuum between them. Some scales will also use descriptors or numeric intervals between the endpoints to assist the individual in grading responses. Commonly a visual analog line of 10 centimeters (100 millimeters) is used. The patient is asked to bisect the line at a point representing self-reported position on the scale. The patient's score is then obtained by measuring from the zero mark to the mark bisecting the scale.

Examples of the use of visual analog scales in rehabilitation settings may be to measure pain, dyspnea, function, or satisfaction with care. Since visual analog scales include a true zero and equal intervals (e.g., mm) they may be analyzed as ratio measures. In contrast, some clinicians may use a numeric rating scale (e.g., rate your function on a scale from 0 to 10) to measure similar impairments. Although providing a numeric rating may be quicker to obtain in clinical settings, scores obtained may not represent interval or ratio data as the reporting of a numeric value may not represent equal intervals. For example, a 4 reported by a patient may not be twice as much function as a 2 reported by another patient. This is due to the nature of interval and ratio scales because a ratio scale allows for the comparison of scores using addition, subtraction, multiplication, or division and an interval scale allows for the comparison of scores using addition or subtraction. These mathematical functions cannot be performed with ordinal or nominal scores.

Knowledge of the level of measurement is important in analyzing data from groups of patients, such as a rehabilitation unit wishing to summarize the functional status of patients admitted during a specified time period. For interval and ratio measures, means and standard deviations may be calculated (assuming the data follow a normal distribution). For ordinal measures, medians and interquartile ranges are appropriate, whereas nominal measures should be reported as modes or frequency counts.

Clearly, the single most important consideration in examining functional status is using the test results correctly to establish and revise the anticipated goals and expected outcomes of intervention and the plan of care. The therapist should carefully delineate the contributing factors that result in the functional deficit. When diminished ability is evident, the therapist must attempt to ascertain the cause of the problem. Some important questions to ask include the following:

1. What are the normal movements necessary to perform the task?

2. Which impairments inhibit performance or completion of the task? For example, do factors such as poor motor planning and execution, decreased strength, decreased range of motion, or altered joint integrity impede function? Does fatigue hamper functional ability?

3. Are the patient's functional deficits the result of impaired communication, perception, vision, hearing, or cognition?

Examples of the kinds of questions a therapist must pose to assess function and integrate findings into a comprehensive treatment program are found using the case vignettes in Table 8.4:

Although the activity limitation in each case is in fact identical, the contributing factors, goals and outcomes, and the interventions would be markedly different. In case A, the patient's inability to transfer can reasonably be attributed to decreased strength. When ameliorated, it is likely that the patient will go on to achieve an outcome of independent ambulation with a prosthesis. The patient in case B has factors that cannot be addressed solely through physical therapy. In addition, it may be difficult to determine whether it is the paralysis or the aphasia that compromises efforts to assess and improve function. Although a similar goal of independence in wheelchair mobility and transfers may be proposed, reexamination throughout the episode of care may demonstrate that functional deficits persist, despite improvement in motor function. In that case, the impairments in comprehension and language function may be the more important factors contributing to functional limitation. Thus, the design of rehabilitation programs is based on the impairments that presumably underlie the functional deficits. If remediation of the impairment does not solve the functional problem, the therapist needs to reexamine the initial clinical impression by looking for other potentially causative factors.

Some functional tasks may need to be analyzed more precisely. Activities can be broken down into subordinate parts, or subroutines. A subordinate part is defined as an element of movement without which the task cannot proceed safely or efficiently. For example, bed mobility includes the following subordinate parts: (1) scooting in bed (changing position for comfort or skin care and getting to the edge), (2) rolling onto the side, (3) lowering the legs, (4) sitting up, and (5) balancing at the edge of the bed. A functional loss of independent bed mobility may result from an inability to perform any or all of these subroutines. These are not only checkpoints for examining patients, but they also later represent the anticipated goals of various interventions. The more involved the patient, the slower the learner, or complex the task, the more the functional task may need to be broken down into subordinate parts.

Determining the Quality of Instruments

Within the rehabilitation setting, many tools exist for the measurement of function or its components. For example, the Catalog of Tests and Measures in APTA's Guide to Physical Therapist Practice includes close to 500 tests and measures.²⁴ In deciding which measure to use the instrument's reliability and validity should be considered. If the reliability and validity of an instrument have not been established, little faith can be put in the results obtained or in the conclusions drawn from the results. A poorly constructed instrument can produce data that are questionable, if not worthless. In light of the fact that the viability of physical therapy as a reimbursable service rests on the demonstration of functional outcomes, the importance of these concepts to functional testing becomes clear. In accordance with APTA's Standards of Measurement, physical therapists should use only those instruments whose reliability and validity are known.²⁵ Although no instrument will have perfect reliability or validity, therapists must be able to gauge the certainty of their data and the appropriate scope of inferences drawn from the data.

Reliability

A reliable instrument measures a phenomenon dependably, time after time, accurately, predictably, and without variation. If a functional test is not reliable, the patient's initial baseline status or the true effect of treatment can be concealed. An instrument with acceptable test–retest reliability is stable and will not indicate change when none has occurred. Tests performed by the same therapist of the same performance should be highly correlated (intrarater reliability). Instruments should also have strong interrater reliability, or agreement among multiple observers of the same event. If a particular patient is examined by several therapists in the course of treatment, or reexamined over time to determine long-term change, the reliability of the functional tool must be known.

A flaw in the clinical use of most types of standardized tests and measures is the tendency to disregard interrater reliability. To use functional tests with maximum accuracy, (1) scoring criteria must be defined clearly and must be mutually exclusive; (2) criteria must be strictly applied to each clinical situation; and (3) all therapists in a facility must be retrained periodically in the use of the instrument to ensure similarity.

Values for reliability coefficients have been recommended. For example, Portney and Watkins suggest less than 0.50 as poor reliability, 0.50 to 0.75 as moderate reliability, and greater than 0.75 as good reliability.^{26, p. 82} These cutoffs must be based on the precision of the measured variable and how the results of the reliability test will be applied. A clinician should use these values as guidelines, and not as absolutes, in determining the accuracy of the measurement and needs to consider the use of the instrument. If high precision is needed in the instrument for clinical decision making, values of a reliability coefficient higher than the minimal threshold for "good" reliability should be used. In addition to the value of the reliability coefficient, the clinician should consider the variability of the measurement that may be expressed as a standard deviation (SD) or confidence interval (CI).

Validity

Validity is a multifaceted concept and established in many different ways. Questions regarding an instrument's validity attempt to determine (1) whether an instrument designed to measure function truly does just that; (2) what the appropriate applications of the instrument are; and (3) how the data should be interpreted. First, the valid instrument should, on the face of it, appear to measure what it purports to measure (face validity).^25,26 For example, an instrument claiming to measure balance should appear to measure some aspect of balance. Another critical dimension is whether the assessment instrument measures all the important or specified dimensions of function (content validity). If there were a gold standard (an unimpeachable measure of a phenomenon, such as a laboratory test with normative values), then a new instrument could be tested against the results of this standard (criterion-related validity). Such a gold standard does not exist for functional instruments. New functional measurement tools can, however, be compared to existing ones that are accepted measures of the same functional activities. The degree to which the two instruments agree helps to establish concurrent validity. Concurrent validity can also be demonstrated by showing that an instrument corresponds appropriately to measures of other phenomena. This method is particularly relevant for self-report instruments. The concurrent validity of some self-report instruments has been determined by comparison with clinician ratings and other clinical findings; for example, a person's level of function as indicated by an instrument correlates directly with clinician's ratings of improvement and inversely with the patient's reports of pain.

Sensitivity and Specificity

In the comparison of a test of function to a gold standard or to another existing instrument one should be concerned with the ability of the measure to make an accurate classification. Sensitivity of a test refers to the proportion of individuals with a limitation in function (as identified by the gold standard or existing instrument) who are correctly classified. In other words, sensitivity is an indication of how well a test identifies persons who should have a positive finding on the test. In contrast, specificity of a test refers to the proportion of individuals who do not have a limitation in function who are correctly classified. Additional properties of a test are the positive predictive value and the negative predictive value. The positive predictive value is the proportion of people who have a positive finding on a test who actually have a limitation in function as classified by the comparison test; the negative predictive value is the proportion of people who have a negative finding on a test who do not have a limitation in function.

Both sensitivity and specificity are expressed as values between 0 and 1. Ideally, both sensitivity and specificity should be as close to 1 as possible, but this is very rare in reality. Different tests, however, will be better at identifying those with the condition and others will be better at identifying those without the condition. This will be reflected in the magnitude of their sensitivity and specificity scores. When values of sensitivity or specificity are close to 1, the SpPIn and SnNOut acronyms may help with interpretation.²⁷ The acronym SpPIn refers to tests that have very high specificity: a positive finding helps to rule in the condition. SnNOut, on the other hand, refers to tests that have very high sensitivity: a negative finding helps to rule out the condition. In general, sensitivity and specificity values greater than 0.95 are considered very high.

Sensitivity and specificity values may be combined to obtain a likelihood ratio (LR) with the following equations. The calculation of likelihood ratios may be helpful in determining how much the test result influences the identification of a patient's condition or identification of a limitation in function. This is especially helpful in cases when sensitivity and specificity are not high enough to apply the SpPIn and SnNOut rules.

The larger the value of a positive likelihood ratio, the more helpful the finding of a positive test is in identification of the condition. Likewise, the smaller the value of a negative likelihood ratio (e.g., close to zero), the more helpful the finding of a negative test is in ruling out the condition. In contrast, a positive or negative likelihood ratio close to 1 is not helpful in identifying the condition. Likelihood ratios can be helpful in determination of post-test odds through their application in Bayes' theorem (i.e., the pretest odds (the likelihood ratio = the post-test odds).²⁷

There is also the predictive validity of a test or measure, which indicates the likelihood of a subsequent phenomenon or event (e.g., return to work) on the basis of a prior phenomenon (e.g., a baseline measure of function). Finally, the degree to which an instrument measures abstract concepts such as physical mobility or social interaction can be established over time (construct validity). Construct validation, using a variety of statistical procedures, is a never-ending process as our understanding of the construct is further refined as instruments are developed to measure it.

Meaningful Change

In addition to reliability and validity, a measure of functional status should be sufficiently sensitive to reflect meaningful changes in a patient's status. The change should exceed the minimal detectable change (MDC) of the instrument and a minimal clinical important difference (MCID). The MDC can be described as the smallest amount of change in a measurement that exceeds the measurement error of the instrument. A physical therapist should be aware of published MDC values for the instruments used to measure function. A sample of MDC and MCID values is presented in Table 8.5. The clinician should keep in mind that MDC values are specific for the patient population in whom the instrument was investigated.

In cases where MDC values may not exist in the literature, values may be calculated if the reliability coefficient, such as an intraclass correlation coefficient (ICC), and a measure of its variability is known, such as the SD. The following equations present the relationship between the MDC95 (the amount of change with 95% confidence beyond measurement error) and the standard error of the measurement (SEM). The second equation can be used to determine the SEM if the value of the reliability coefficient and the standard deviation (SD) from one of the groups used to determine reliability is known. Note that because the ICC and the SD are from a specific sample, the calculated SEM and MDC95 are only generalizable to persons with similar conditions.

For example, if a study of persons after total knee arthroplasty reported an ICC of 0.75 for knee flexion with an SD of 5 degrees, the SEM is equal to 2.5 degrees. Using this value in the first equation, the MDC95 is 6.925 degrees. In other words, the measure of knee flexion would need to change more than 7 degrees to have 95% confidence that this change was due to something other than measurement error.

The MCID is the smallest difference in a measured variable that signifies an important rather than a trivial difference in the patient's condition. The value of the MCID should exceed the value of the MDC; in other words, the MCID needs to exceed the measurement error. For example, a 50-meter change in distance on the 6-minute walk test may be beyond measurement error; however, is the ability to walk 50 meters during 6 minutes meaningful to an individual patient's function? A number of different ways have been suggested to determine values for the MCID.^{26, pp. 646-652} No universal method exists. Controversies exist among the strategies to determine MCID based on the perspective of what is meaningful, as well as issues related to measurement.^37,38 The clinician should consult the literature for recommended values of the MCID for measures of function. Additionally, online resources are being developed to help clinicians locate values for a number of tests.^39,40 Similar to the interpretation of the MDC, in consulting published values for the MCID for a measure of function the clinician needs to consider the sample for which the values were established.

Considerations in Selection of Instruments

A large number of instruments have been developed to assess and to classify function. Given the plethora of instruments that currently exist, it is quite reasonable to ask how these instruments compare with one another. It is important to remember that no instrument is perfect for all patients or all situations. No instrument can measure all the items potentially relevant to a particular individual and provide the perfect composite picture. For example, one instrument may provide an extensive measure of ADL, but not deal with psychological or social dimensions of function. Another instrument may investigate social functioning while omitting some ADL tasks. Many items overlap from instrument to instrument. For example, a question on the ability to ambulate is a common item found in most physical function instruments. Although instruments may cover the same kind of activity, the questions posed about the performance of the same activity may be quite different. For example, one instrument may investigate the degree of difficulty and of human assistance required to "dress yourself, including handling of closures, buttons, zippers, snaps." Another may ask, "How much help do you need in getting dressed?" As discussed, differences also may exist in the time frames sampled in the various instruments. Critical questions to ask in selecting an instrument are presented in Box 8.2.

Extrapolating items from a variety of instruments may provide the kind of data desired but should be considered with extreme caution inasmuch as this process changes reliability or validity of the measurements. Factors such as the theoretic orientation of the user, the purpose for using the instrument, and the relevance of particular functional items to certain patient populations all enter into the decision making process. In the final analysis, the choice of instrument may be dictated by practical considerations. For example, self-report instruments, which rely on information from the patient, are limited in use to mentally competent individuals. Time and resources for administration also may influence test selection, or some rehabilitation facilities may adopt the use of a specific instrument for all patients (e.g., the Functional Independence Measure [FIM]). In any case, many suitable instruments are available for assessing functional status, some of which are commonly used by clinicians as well as researchers.

Among the factors to consider in selecting a measure of function is whether a single dimension measure or a multidimensional measure should be used. For example, single dimension measures may include a specific construct such as balance, gait, or reaching; whereas multidimensional measures would include a combination of these constructs or have items that represent impairments, activity limitations, and participation restrictions. As an example of a single test, gait speed may be used to represent function. This test may frequently be used in clinical settings because it require a minimal amount of time to perform and little equipment other than a stopwatch and a hallway free of obstructions. For the test, the time for the patient to ambulate a specified distance, such as 10 meters, is recorded and speed is calculated as distance divided by time and frequently reported as meters per second. Although this is a test of a specific mobility item, walking, one might make inferences in regard to a patient's function based on this test. The clinician, however, is responsible to check with the literature to determine if the inferences are supported by evidence, because there are some specific populations where gait speed may be representative of a patient's ability to function. For example, in a study of persons after hip arthroplasty it was demonstrated that gait speed was more representative of the capacity to ambulate than performance because when the patients were tested in real world environments their gait speed was slower than in the clinic. However, in this case the measure of capacity versus performance was highly correlated (= 0.440).⁴¹ Recent evidence among older persons also suggests that the measure of gait speed is highly related to overall health.⁴² For populations that have not been tested, however, a clinician should be cautious in using gait speed to make inferences regarding function.

Other tests may use multiple items to measure a single dimension, such as the items in the Barthel Index to measure ADL or the 14 items in the Berg Balance Scale to calculate a balance score. A clinician is justified using these instruments to describe the dimension of interest related to the patient's problem. However, unless data exist, they should not be used to make inferences regarding other impairments, activity limitations, or participation restrictions. Other instruments specific to those dimensions should be used as appropriate to the patient's presentation.

Alternatively, a clinician may take an approach to understand a patient's health status in all its domains. Further instrument development has resulted in the emergence of multidimensional health status instruments to measure the spectrum of health status more comprehensively. Used in conjunction with traditional clinical methods of examining signs and symptoms, multidimensional functional status instruments can add an important comprehensive view of a patient's function to the overall health status. In this respect they add a crucial, and previously missing, component in evaluating the health of individuals.

Recently, more comprehensive instruments are being developed to measure multiple dimensions of the ICF to present an overall view of a person's function. Specifically, a number of ICF Core Sets are being developed for specific patient conditions, such as stroke,⁴³ or by settings such as postacute rehabilitation settings.⁴⁴ Each core set includes items related to body functions, body structures, activities, participation, and contextual factors important to the specific condition or setting. These core sets are being developed using expert opinion and are being empirically tested to determine if representative items are included.^45,46 These core sets potentially may allow a clinician to focus on the most relevant items from the myriad of specific items in the ICF classification.

The final section of this chapter briefly discusses one single dimension instrument and three multidimensional instruments a physical therapist may use in practice. Many other instruments exist, some of which were mentioned previously in this chapter and some of which are included in other chapters. For a selection of instruments, the reader is referred to the APTA's Catalog of Tests and Measures.²⁴

For the purposes of illustration, three multidimensional instruments, the Functional Independence Measure (FIM), the Outcome and Assessment Information Set (OASIS), and the SF-36 are presented. Choice of a multidimensional instrument carries the same caveats mentioned for instruments a single dimension.⁴⁷ No instrument measures all potentially relevant items. In addition, depending on how an item is worded, items that may appear to measure the same aspect of function may be measuring different aspects of performance.⁴⁸ Table 8.6 presents a comparison of items covered. In the area of physical function, questions on the ability to ambulate are the only items these instruments have in common. Aspects of physical function not covered in any of these instruments include bed mobility and dexterity. The FIM and the OASIS include more ADL items than either the Sickness Impact Profile (SIP) or the SF-36. The SIP and the SF-36 investigate work performance, whereas the FIM and the OASIS do not. This is not surprising, given that the FIM was originally developed as a tool for the inpatient rehabilitation setting and the OASIS was expressly designed for home health agencies, both generally serving older patients. In contrast, the development of the SIP and SF-36 was focused on younger adult populations in ambulatory care. Anxiety and depression are addressed as areas of psychological function in the SIP, the SF-36, and the OASIS, but not in the FIM. The OASIS does not explore social function, whereas the other three instruments do. Finally, only the SF-36 records general health perceptions.

The Barthel Index

The Barthel Index was developed by a physical therapist over 45 years ago.²² Although not as commonly used today in practice as some other instruments, this instrument is still used to measure function in clinical research, and this assessment tool represents one of the earliest contributions to the functional status literature and identifies physical therapists' long-standing inclusion of functional mobility and ADL measurement within their scope of practice. The Barthel Index specifically measures the degree of assistance required by an individual on 10 items of mobility and self-care ADL (Table 8.7). Levels of measurement are limited to either complete independence or needing assistance. Each performance item is scored on an ordinal scale with a specified number of points assigned to each level or ranking. Variable weightings were established by the developers of the Barthel Index for each item based on clinical judgment or other implicit criteria. An individual who uses human assistance in eating, for example, would receive 5 points; independence in eating would receive a score of 10 points. A single global score, ranging from 0 to 100, is calculated from the sum of all weighted individual item scores, so that 0 equals complete dependence for all 10 activities, and 100 equals complete independence in all 10 activities. The Barthel Index has been used widely to monitor functional changes in individuals receiving inpatient rehabilitation, particularly in predicting the functional outcomes associated with stroke.^49,50 Although its psychometric properties have never been fully examined, the Barthel Index has demonstrated strong interrater reliability (0.95) and test–retest reliability (0.89), as well as high correlations (0.74 to 0.80) with other measures of physical disability.⁵¹

The Functional Independence Measure

The Functional Independence Measure (FIM)^52,53 is an 18-item measure of physical, psychological, and social function that is part of the Uniform Data System for Medical Rehabilitation (UDSMR).⁵⁴ The UDSMR collects data from participating rehabilitation facilities and issues summary reports of the records that have been entered into the UDSMR database. The FIM uses the level of assistance an individual needs to grade functional status from total independence to total assistance (Fig. 8.5). A person may be regarded as independent if a device is used, but this is recorded separately from "complete" independence. The instrument lists six self-care activities: feeding, grooming, bathing, upper body dressing, lower body dressing, and toileting. Bowel and bladder control, aspects of which some may consider as impairments rather than function, are categorized separately. Functional mobility is tested through three items on transfers. Under the category of locomotion, walking and using a wheelchair are listed equivalently, whereas stairs are considered separately. The FIM also includes two items on communication and three on social cognition.

The FIM measures what the individual does, not what that person could do under certain circumstances. The interrater reliability of the FIM has been established at an acceptable level of psychometric performance (intraclass correlation coefficients ranging from 0.86 to 0.88).⁵³ The face and content validity of the FIM, as well as its ability to capture change in a patient's level of function, have also been determined. Any clinical worker can administer the FIM after appropriate training in using the response set for each item.

For persons with stroke, the motor scale of the FIM has been shown to have high concurrent validity with the Barthel Index (ICC ≥ 0.83).⁵⁵ Gosman-Hedstrom and Svensson⁵⁶ have shown strong construct validity between items on the Barthel and items on the FIM that measure functional limitations. Rasch analysis has been applied to the scale scores of the FIM, which are ordinal measures, in order to create interval scale measurements.⁵⁷ In addition, the WeeFIM, an 18-item instrument based on the FIM, has been developed for use for children between the ages of 6 months and 18 years.⁵⁸

The Outcome and Assessment Information Set

The Outcome and Assessment Information Set (OASIS) was designed to ensure the collection of pertinent data on the adult patient in the home care setting that would allow home health agencies to assess the quality of care by measuring the outcomes of care.^59,60 During the years of its initial development, use of the OASIS by home health agencies had been voluntary. However, as of January 1, 1999, home health agencies were mandated to use the OASIS as a Condition of Participation in the Medicare program by the Health Care Financing Administration. The current version of OASIS, known as OASIS-C, contains core items covering sociodemographic characteristics, environmental factors, social support, health status, and functional status.⁶¹ This version of the instrument was approved in 2009 and represents a substantial change from preceding versions. OASIS is not designed to be a comprehensive examination of a patient or an "add-on" measurement. OASIS items are meant to be integrated into the clinical record to highlight various aspects of a patient's status that identify particular needs for care on admission to the home health service, at follow-up every 60 days, and at discharge. The OASIS was intended to be a discipline-neutral record, administered by any health professional, including physical therapists. Created as part of a research program to develop outcome measures applicable to home health, the OASIS has been field-tested through demonstration projects and refined by a panel of experts. Reliability testing is ongoing.

Ease of administration increases with familiarity with the instrument. Unlike most other instruments, the response sets that accompany each item are specifically matched to the item. Some response sets have only two possible descriptions of behavior, whereas others have as many as nine possible descriptions of behavior. Therefore, the user must be familiar with the possible response set to each item and anticipate that comfort level in using this instrument will increase over a learning curve. The ADL/instrumental ADL (IADL) section is composed of 13 different items (Table 8.8): grooming, dressing the upper body, dressing the lower body, bathing, transferring to the toilet, toileting, transfers, ambulation/locomotion, feeding, meal preparation, ability to use the telephone, prior functioning, and falls risk.

The SF-36

The SF-36 contains 36 items based on questions used in the RAND Health Insurance Study. These 36 items were culled from the 113 questions used by RAND in the Medical Outcomes Study (MOS) to explore the relationship between physician practice styles and patient outcomes.⁶² Thus, it was named the SF-36, because it was a short form of the MOS instrument with only 36 questions. The MOS provided important data on the functional status of adults with specific chronic conditions⁶³ and the well-being of patients experiencing depression compared to subjects with a chronic medical condition.⁶⁴ The SF-36 demonstrated high reliability and validity (correlation coefficients ranging from 0.81 to 0.88).^65,66,67,68 Normative data for these self-report items have been collected.⁶⁹

All but one of the 36 questions of the SF-36 are used to form eight different scales: physical function, social function, role function, mental health, energy/fatigue, pain, and general health perceptions. The last question considers self-perceived change in health during the past year. Items are scored on nominal (yes/no) or ordinal scales. Each possible response to an item on a scale is assigned a number of points. The total points for all items within a scale are then added and transformed mathematically to yield a percentage score, with 100% representing optimal health. Sample items on physical function and role function are presented in Table 8.9. The SF-36 has been used in a number of studies that describe the health status and physical functioning of patients with a variety of impairments receiving physical therapy services.^{70,71,72,73,7475}

A shortened version has been developed that uses a subset of items from the SF-36.⁷⁶ This version, known as SF-12, includes items from each of the eight concepts represented in the SF-36 and allows for the calculation of physical and mental subscale scores. An advantage to using fewer questions is that less time is required to complete the survey. This, however, may be at the expense of having a less precise score that may not be as sensitive to change for an individual patient.⁷⁷ The development of the SF-36 stands as the premier example, to date, of a complete and published exploration of the psychometric properties of an instrument as an essential part of its development, and a testament to the responsibility of its creators in verifying the quality of the SF-36 as a scientific tool (Box 8.3 Evidence Summary).

This chapter has presented a conceptual framework for understanding function and for the examination of functional status. The traditional medical model, with its narrow focus on disease and its symptoms, fails to consider the impact of the condition on the person, as well as the broader social, psychological, and behavioral dimensions of illness. All these factors have an impact on an individual's activity and participation. Although individual aspects of function may be assessed, examination of functional status must be viewed as a broad, multidimensional process. Finally, specific aspects of functional examination have been discussed, including purpose, selection of instruments, aspects of test administration, interpretation of test results, and determination of instrument quality.

Questions for Review

1. How does the measurement of function relate to health status?

2. Your rehabilitation facility uses the FIM. How can reliability be ensured so that the results can be used with confidence in both treatment planning and research?

3. What criteria can be used in the selection of a functional instrument?

4. Discuss the uses, advantages, and disadvantages of performance-based instruments, interviewer reports, and self-administered reports.

5. Explain how environment, fatigue, and other related issues affect measurement of function. Suggest ways to control these factors in the clinic.

6. Identify the major types of scoring systems used in functional instruments. What are some common errors in interpretation of testing results?

7. Review Tables 8.4, 8.6, 8.7, and 8.8. Hypothesize a caseload in a particular setting and indicate how and when you could use each of these instruments with the proposed population. Describe the advantages and disadvantages of each. Imagine that you are looking to follow the progress of these same patients to another setting. Which instruments would you choose?

8. Using one of the instruments, develop a set of results and use them to identify treatment goals and outcomes and to formulate a plan of care.

9. For each of the following, identify particular physical tasks relevant to that individual's functional status:

   • A 22-year-old female file clerk

   • A 31-year-old male physical therapist assistant

   • A 39-year-old female homemaker with children

   • A 45-year-old male construction worker

   • A 56-year-old female school teacher

   • A 65-year-old male journalist

10. Discuss the relationship among disease, body structures, body functions, activity, participation, environmental factors, and personal factors.

A 78-year-old woman with a diagnosis of osteoarthritis was admitted for a right total hip replacement. The patient reported a long-standing history of discomfort. She described the hip pain as radiating posteriorly to the buttock and low back and exacerbated by weight-bearing and stair climbing. Over the past 12 months she has experienced a very marked increase in pain and stiffness. Radiographic findings demonstrated degenerative changes of both the acetabulum and femoral head consistent with osteoarthritis. The surgical intervention replaced the right femoral head and neck with a metallic prosthesis and the acetabulum was resurfaced with a plastic cup. Past medical history is unremarkable.

SOCIAL HISTORY

The patient is a retired manager of a small accounting firm that she and her husband established. Her husband is deceased. She has three grown children who all live in neighboring communities. Before the functional limitations imposed by the hip pain, the patient had been independent in all ADL and IADL. She also volunteered her accounting services 1 day per week to a local charity that provides meals to homebound individuals. She was a regular participant in family outings, enjoyed going to the theater, concerts, and special museum events, and was an active member of the community historical preservation society. Recently, these activities had to be curtailed owing to the increased hip discomfort. She essentially had no activities outside the home for 3 months before admission and used a walker to minimize weight-bearing and reduce pain. She also required the assistance of a home care aide 4 hours a day two times per week (primarily for shopping, errands, and some household management tasks). She expressed considerable distress at being unable to take a bath and having to rely on the assistance of another person for some basic care activities. She had been using aspirin for its analgesic and anti-inflammatory effects. However, the pain experienced in recent months was not alleviated by the aspirin and other conservative measures. She has been instructed to use local applications of heat, periodic rest intervals, and gentle range-of-motion (ROM) exercises. The patient has extensive medical insurance coverage and is without financial concerns.

POSTSURGICAL RIGHT HIP PRECAUTIONS

No hip flexion beyond 90°.

Avoid crossing one leg or ankle over the other.

Avoid internal rotation of right lower extremity.

REVIEW OF SYSTEMS

Communication, Affect, Cognition, Learning Style: Fully communicative and oriented × 3.

Cooperative and motivated. Hearing intact. Wears corrective lens; experiences "night blindness," which she describes as seeing poorly in dim light and her eyes take several seconds longer than normal to adjust from brightness to dimness.

Cardiopulmonary: Heart rate (HR) = 84 beats/minute; blood pressure (BP) = 130/78 mm Hg; respiratory rate (RR) = 16 breaths/minute; no appreciable increases with activity.

Integumentary: Surgical wound healing well; staples removed.

Strength: Upper extremity gross ROM is within normal limits (WNL). Gross strength generally good to normal, except hands. Left hip, knee, and ankle at least good on break test. Partial weight-bearing on right lower extremity.

Joint Integrity and Mobility: Patient reports some sporadic episodes of wrist and finger stiffness on awakening in the morning and after periods of immobility. Crepitus noted in right knee. Heberden's nodes noted at the distal interphalangeal (DIP) and proximal interphalangeal (PIP) joints of the left index finger.

Range of Motion: Right knee and ankle within functional limits; right hip not tested.

Muscle Performance: Grip strength is reduced bilaterally (4–15).

Pain: Patient denies pain in wrist or fingers, or right hip.

Gait, Locomotion, and Balance: The patient is ambulating on level surfaces with supervision using bilateral standard aluminum axillary crutches with partial weight-bearing on the right lower extremity. Stair climbing also requires minimal assistance. It is anticipated that the patient will be independent with ambulation on level surfaces at time of discharge from the hospital.

Functional Status: Impaired bed mobility (modified independence device), sit-to-stand, transfers (minimum assistance).

Home Environment: The patient lives alone in a fifth-floor apartment in a building with an elevator. The living space is a one-bedroom apartment on a single level.

Patient Goals: The patient is extremely motivated to once again be an independent manager of her personal care and household management needs. The prosthetic replacement has successfully relieved much of the pain experienced in the hip before surgery (most of her current discomfort is described as minor and associated with the surgical incision). She would also like to return to her family, volunteer, social, and leisure activities. She is very determined to discontinue the home care assistance as soon as possible.

1. Based on the findings of the initial examination, discuss the links between the condition, impairments in body structures and body functions, activity limitations, participation restrictions, and contextual factors using the ICF model.

2. Identify the specific ADL and IADL skills that would need to be examined to return this patient to the highest level of function and achieve the patient's goals for rehabilitation. Discuss the appropriateness of the instruments presented in this chapter for measuring her function and documenting the outcomes of patient management.