Skip to main content
. 2006 Jan 5;66(1):34–45. doi: 10.1136/ard.2005.044354

Table 2 Categories of evidence16.

Ia Evidence from meta‐analyses 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 type of quasi‐experimental study
III Evidence from descriptive studies, such as comparative, correlation, or case–control
IV Evidence from expert committee reports or opinions or clinical experience of respected authorities, or both