Failure to adopt beneficial therapies caused by bias in medical evidence evaluation

Background. Although it is known that many evidence-based therapies are underutilized, the causes of the research-practice gap are not well understood. The authors sought to determine if there is a bias in the evaluation of new evidence that leads to low rates of adoption of beneficial therapies compared to abandonment of harmful ones. Methods. Two case vignettes describing hypothetical clinical trials were administered to 2 independent samples of pulmonary and critical care practitioners. Each vignette was presented in 2 different ways; in one version, the results of the hypothetical trial showed that a treatment was harmful, and in the other version, the same treatment was shown to be beneficial. Prospective respondents from each sample were randomized to receive 1 version of each vignette (intersubject design). The main outcome was respondents' willingness to apply the results of the hypothetical trial to patient care. Results. There were 174 participants for trial 1 and 138 participants for trial 2 (enrollment rates of 44.2% and 41.8%, respectively). For trial 1, respondents were 2.3 times less likely to change clinical practice based on results indicating benefit as opposed to harm (33.3% v. 76.5%; P < 0.0001). Similarly, for trial 2, respondents were 2.57 times less likely to change practice when trial results showed that early use was beneficial as opposed to showing that early use was harmful (37.1% v. 95.3%; P < 0.0001). Conclusions. When evaluating clinical trials, physicians demonstrate less willingness to adopt beneficial therapies than to abandon harmful ones. This difference may contribute to the research-practice gap.