Trial design can lead to biased estimates of intervention effect, but studies have inconsistently identified which design aspects are associated with the greatest risk of bias. This study combined data from 234 unique meta-analyses involving 1973 trials to estimate associations of specific trial characteristics with average bias and between-trial heterogeneity. Intervention effect estimates seemed to be exaggerated in trials with inadequate or unclear random-sequence generation, allocation concealment, or double-blinding. However, these observations occurred primarily in trials with subjective outcomes, with little evidence of bias in trials with objective outcomes, such as mortality.
Topics:
clinical trials, heterogeneity, bias (epidemiology), costa rica, intervention studies, randomized controlled trial, ...
Ann Intern Med. 2012;157(6):429-438. doi:10.7326/0003-4819-157-6-201209180-00537