Evidence reversals in primary care research: a study of randomized controlled trials.

We studied the extent to which evidence from randomized controlled trials (RCTs) relevant to primary care is contradicted in subsequent research. When it was, we identified this event as an evidence reversal. In addition, we sought to identify characteristics of RCTs associated with their reversal. From 408 RCTs published during the period 2002­2005, study characteristics such as sample size were identified and extracted. Subsequently, we compared the evidence reported in each of these RCTs with the evidence on that same topic in an online summary resource in 2019. This allowed us to classify each RCT in one of the following 3 categories: evidence confirmed, reversed, or uncertain if this evidence is confirmed or reversed. Over 12­17 years of follow-up time, the findings of about 9 in 10 RCTs summarized as POEMs are stable. We found no statistically significant associations between trial characteristics and their subsequent reversal. This low rate of evidence reversal is good news for the RCTs that are used to inform decision-making.