Chapter 7: Appraising Research Studies of Systematic Reviews

Pre-Test

1. Describe the differences between a systematic review and a narrative review.

2. State three differences between systematic reviews and randomized clinical trials.

3. What elements of a systematic review impact applicability to a searchable clinical question?

4. What is the PEDro scale and how can it be used in a systematic review?

5. How are systematic reviews used to inform clinical practice?

Introduction

What is a Systematic Review?

Systematic reviews are a special type of research study characterized as secondary research. Secondary research studies are "studies of studies" that summarize information from multiple primary studies. Primary studies are "original studies," such as the randomized clinical trials and cohort studies described in previous chapters. Systematic reviews are the principal scientific method for secondary research. Systematic reviews are developed using a documented, systematic approach that minimizes bias.¹ Authors of a systematic review define a specific purpose for the study. Methods that minimize bias are determined prior to the beginning of the study. Unlike a randomized clinical trial, a systematic review does not include recruiting and enrolling participants. Specific inclusion and exclusion criteria are used to select appropriate studies for review. The sample size for a systematic review is the number of studies identified that meet the specific criteria.

Systematic reviews of treatment interventions are most common; however, reviews can also appraise diagnostic tests, outcome measures, and prognostic factors. For example, Dessaur and Magarey² conducted a systematic review of diagnostic studies to determine the diagnostic accuracy of clinical tests for superior labral anterior-posterior lesions in the shoulder. In another example, Blum and Korner-Bitensky³ conducted a systematic review of studies of the Berg Balance Scale to better understand its usefulness in stroke rehabilitation. In this chapter, we focus on systematic reviews of intervention studies; however, the same principles and appraisal processes can be applied to other types of systematic reviews (Fig. 7.1).

A meta-analysis is a statistical method used to summarize outcomes across multiple primary studies, usually as a part of a systematic review. The sample size of a meta-analysis is considered the total number of participants from all studies combined. Not all systematic reviews contain a meta-analysis. This analysis depends on the nature of the data included in the selected primary studies. In a meta-analysis, data are "normalized" across studies and the results are expressed as a quantitative value representing all included studies (e.g., effect size; see Chapter 4).

Narrative reviews provide an overview of literature and are commonly published in peer-reviewed research journals. These reports are sometimes confused with systematic reviews. A narrative review is not a systematic study and analysis of the literature.^4,5 Rather, it is a description of the content ...