GRADE guidelines: 7. Rating the quality of evidence--inconsistency.

TitleGRADE guidelines: 7. Rating the quality of evidence--inconsistency.
Publication TypeJournal Article
Year of Publication2011
AuthorsGuyatt GH, Oxman AD, Kunz R, Woodcock J, Brozek J, Helfand M, Alonso-Coello P, Glasziou P, Jaeschke R, Akl EA, Norris S, Vist G, Dahm P, Shukla VK, Higgins J, Falck-Ytter Y, Sch├╝nemann HJ
Corporate AuthorsGRADE Working Group
JournalJournal of clinical epidemiology
Volume64
Issue12
Pagination1294-302
Date Published2011 Dec
ISSN1878-5921
KeywordsConfidence Intervals; Evidence-Based Medicine; Humans; Observer Variation; Practice Guidelines as Topic; Randomized Controlled Trials as Topic; Research Design; Sample Size
Abstract

This article deals with inconsistency of relative (rather than absolute) treatment effects in binary/dichotomous outcomes. A body of evidence is not rated up in quality if studies yield consistent results, but may be rated down in quality if inconsistent. Criteria for evaluating consistency include similarity of point estimates, extent of overlap of confidence intervals, and statistical criteria including tests of heterogeneity and I(2). To explore heterogeneity, systematic review authors should generate and test a small number of a priori hypotheses related to patients, interventions, outcomes, and methodology. When inconsistency is large and unexplained, rating down quality for inconsistency is appropriate, particularly if some studies suggest substantial benefit, and others no effect or harm (rather than only large vs. small effects). Apparent subgroup effects may be spurious. Credibility is increased if subgroup effects are based on a small number of a priori hypotheses with a specified direction; subgroup comparisons come from within rather than between studies; tests of interaction generate low P-values; and have a biological rationale.

DOI10.1016/j.jclinepi.2011.03.017
Alternate JournalJ Clin Epidemiol