Table 2AHCPR derived categories of evidence

Ia:evidence from meta-analysis of randomised controlled trials
Ib:evidence from at least one randomised controlled trial
IIa:evidence from at least one controlled study without randomisation
IIb:evidence from at least one other type of quasi-experimental study
III:evidence from non-experimental descriptive studies, such as comparative studies, correlation studies and case-control studies
IV:evidence from expert committee reports or opinions and/or clinical experience of respected authorities

From: Methods

Cover of Dyspepsia
Dyspepsia: Managing Dyspepsia in Adults in Primary Care.
NICE Clinical Guidelines, No. 17.
North of England Dyspepsia Guideline Development Group (UK).
Newcastle upon Tyne (UK): University of Newcastle upon Tyne; 2004 Aug 1.
Crown Copyright © 2004.

PubMed Health. A service of the National Library of Medicine, National Institutes of Health.