Chapter 7

Reviews

Overview

A review article or meta-analysis carefully gathers all prior publications on a specific topic and summarizes them to provide a big-picture analysis.

Steps:

1.An extensive search of the literature

2.Extraction of key information from relevant articles

3.Clear and concise presentation of this information

Benefits

• A literature review is an effective way to become an expert in the literature on a well-defined topic

• A literature review is a helpful step in preparing for future primary or secondary analyses

• Review articles are often cited more often than reports of individual field studies

Limitations

• Not all journals publish review articles (especially reviews that the editors do not solicit)

• Reviews are sometimes perceived to be a less rigorous form of research than projects that collect new data and/or involve statistical analysis

Selecting a Topic

• The most important decision is to select a topic that is narrow enough that all the relevant publications can be acquired.

• The topic may need to be modified after a preliminary search, depending on the number of articles available.– 8 = too few → expand the scope– 352 = too many → narrow the scope

Library Access

• The full text of every relevant article must be identified and obtained.

• Check with a university librarian about the library’s policies and the fees that may be charged for the use of interlibrary loan services.

• Maintain a meticulous system for tracking articles that have already been acquired, those that have been requested but not yet received, and those that need to be requested.

Narrative Reviews

• Narrative reviews tell a “story” about a well-defined topic using evidence from the literature to support the “plot”

• Narrative reviews must be carefully organized by theme, methodology, chronology, or some other guiding principle

• The absence of a systematic search strategy must be justified by the researcher

Systematic Reviews

• Systematic reviews are designed to minimize the bias that might occur when review article authors handpick the articles they want to highlight

• After the identification of the study question, the most important decision in a systematic review is the selection of keywords and inclusion criteria

• The goal is to craft a search strategy that identifies all the articles ever published on the narrow, well-defined area covered by the review

Systematic Reviews

• Once the articles are identified from one or more abstract databases, each article is screened to see whether it is eligible for inclusion.

• Relevant information is extracted from all eligible articles and presented in table form.

• Then the trends and key observations are summarized.

Meta-Analysis

• The goal of a meta-analysis is to combine the results of several high-quality articles that used similar methods to collect and analyze data into one summary statistic.

• Meta-analysis usually begins with a comprehensive systematic review of the literature to identify every single possibly relevant article.

Meta-Analysis

• The inclusion criteria for a meta-analysis are usually more restrictive than they are for systematic reviews.

• These restrictions are important because a summary statistic is only meaningful when every study included in the meta-analysis has very similar definitions for exposures and outcomes, similar study designs and methods, and similar populations.

• Trying to combine dissimilar studies could hide real and meaningful differences among populations.

Meta-Analysis

The steps of a meta-analysis are to:•Conduct a systematic review•Assess the quality and comparability of each eligible study•Extract statistical results from each study that meets all inclusion criteria •Combine these statistical results into one summary statistic

FIGURE 7-1 Key Characteristics of Reviews and Meta-Analyses

FIGURE 7-1 Key Characteristics of Reviews

and Meta-

Analyses