tailieunhanh - Báo cáo y học: "Delta inflation: a bias in the design of randomized controlled trials in critical care medicine"

Tuyển tập các báo cáo nghiên cứu về y học được đăng trên tạp chí y học quốc tế cung cấp cho các bạn kiến thức về ngành y đề tài: Delta inflation: a bias in the design of randomized controlled trials in critical care medicine. | Aberegg et al. Critical Care 2010 14 R77 http content 14 2 R77 RESEARCH Open Access Delta inflation a bias in the design of randomized controlled trials in critical care medicine Scott KAberegg 1 D Roxanne Richards2 and James M O Brien3 Abstract Introduction Mortality is the most widely accepted outcome measure in randomized controlled trials of therapies for critically ill adults but most of these trials fail to show a statistically significant mortality benefit. The reasons for this are unknown. Methods We searched five high impact journals Annals of Internal Medicine British Medical Journal JAMA The Lancet New England Journal of Medicine for randomized controlled trials comparing mortality of therapies for critically ill adults over a ten year period. We abstracted data on the statistical design and results of these trials to compare the predicted delta delta the effect size of the therapy compared to control expressed as an absolute mortality reduction to the observed delta to determine if there is a systematic overestimation of predicted delta that might explain the high prevalence of negative results in these trials. Results We found 38 trials meeting our inclusion criteria. Only 5 38 of the trials provided justification for the predicted delta. The mean predicted delta among the 38 trials was and the mean observed delta was P resulting in a delta-gap of . In only 2 38 of the trials did the observed delta exceed the predicted delta and only 7 38 of the trials demonstrated statistically significant results in the hypothesized direction these trials had smaller delta-gaps than the remainder of the trials delta-gap versus P . For trials showing non-significant trends toward benefit greater than 3 large increases in sample size 380 - 1100 would be required if repeat trials use the observed delta from the index trial as the predicted delta for a follow-up study. Conclusions Investigators of therapies .