GRADE guidelines: 8. Rating the quality of evidence--indirectness.

TitleGRADE guidelines: 8. Rating the quality of evidence--indirectness.
Publication TypeJournal Article
Year of Publication2011
AuthorsGuyatt GH, Oxman AD, Kunz R, Woodcock J, Brozek J, Helfand M, Alonso-Coello P, Falck-Ytter Y, Jaeschke R, Vist G, Akl EA, Post PN, Norris S, Meerpohl J, Shukla VK, Nasser M, Sch├╝nemann HJ
Corporate AuthorsGRADE Working Group
JournalJournal of clinical epidemiology
Date Published2011 Dec
KeywordsBias (Epidemiology); Clinical Competence; Evidence-Based Medicine; Humans; Meta-Analysis as Topic; Practice Guidelines as Topic; Randomized Controlled Trials as Topic; Review Literature as Topic

Direct evidence comes from research that directly compares the interventions in which we are interested when applied to the populations in which we are interested and measures outcomes important to patients. Evidence can be indirect in one of four ways. First, patients may differ from those of interest (the term applicability is often used for this form of indirectness). Secondly, the intervention tested may differ from the intervention of interest. Decisions regarding indirectness of patients and interventions depend on an understanding of whether biological or social factors are sufficiently different that one might expect substantial differences in the magnitude of effect. Thirdly, outcomes may differ from those of primary interest-for instance, surrogate outcomes that are not themselves important, but measured in the presumption that changes in the surrogate reflect changes in an outcome important to patients. A fourth type of indirectness, conceptually different from the first three, occurs when clinicians must choose between interventions that have not been tested in head-to-head comparisons. Making comparisons between treatments under these circumstances requires specific statistical methods and will be rated down in quality one or two levels depending on the extent of differences between the patient populations, co-interventions, measurements of the outcome, and the methods of the trials of the candidate interventions.

Alternate JournalJ Clin Epidemiol