Systematic Reviews to Answer Health Care Questions

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Chapter 12 • Assessing and Rating the Strength of the Body of Evidence

■ ■ SUMMARY • The final step in the synthesis of a systematic review is evaluating the strength or quality of the body of evidence for specific research questions and outcomes. • The Grades of Recommendation Assessment, Development, and Evaluation (GRADE) is a method to rate the strength of the body of evidence that evaluates specific methodological characteristics of studies. • GRADE domains include study limitations, directness, consistency, precision, and reporting bias for all studies; and magnitude of effect, dose–response association, and plausible con founding for observational studies. • The study limitations domain incorporates both study design and study quality (risk of bias, internal validity). • Directness describes the relevance of the evidence to the PICOTS elements of the research question. • Consistency refers to the degree of similarity of results of different studies in a body of evidence and considers the direction and magnitude of effect. • Precision is the degree of certainty surrounding an estimate of effect for a specific outcome. • Reporting biases include publication bias, outcome reporting bias, and analysis reporting bias. • The overall rating is based on the ratings of the individual domains scored as high, moderate, low, and very low or insufficient. • Information relating to the body of evidence, domain ratings, and the overall strength of evidence rating are summarized in concise tables. A systematic review of the effectiveness of health system interventions to reduce disparities in preventive health services included studies of interventions to increase rates of colorectal cancer screening. 38 In addition to studies of patient navigation discussed in Box 12.1, the systematic review included other types of interventions including outreach activities, such as telephone calls and prompts; educational videos; a screening checklist for clinicians; and clinician train ing. No statistical meta-analysis was conducted for these studies because of high clinical het erogeneity. Using the AHRQ ECP approach, the research team graded the strength of evidence domains as indicated in Table 12.5. 1. Based on the grade definitions (Table 12.3) and information provided from the systematic review (Table 12.5), what overall strength of evidence grade should be assigned to each type of intervention? 2. What supporting information justifies the strength of evidence grades assigned in ques tion 1? CASE STUDY: Grading Strength of Evidence

3. Based on results of the systematic review, which intervention(s) have sufficient evidence of effectiveness and could be recommended to a health system to increase colorectal cancer screening rates? 4. Based on results of the systematic review, which intervention(s) lack evidence of effective ness and should not be recommended? Copyright © 2024 Wolters Kluwer, Inc. Unauthorized reproduction of the content is prohibited.