A measurement framework for adherence in patient decision aid trials applied in a systematic review subanalysis

OBJECTIVE:To explore how studies of decision aids conceptualize and measure adherence and to evaluate the effect of patient decision aids on adherence. STUDY DESIGN AND SETTING:A subanalysis of adherence studies included in the 2014 Cochrane review on patient decision aids. An adherence framework for decision aid trials is presented which includes two types of adherence: "adherence to choice" and "adherence to treatment." Included studies were classified based on the adherence framework, and their impact on adherence was assessed. RESULTS:Thirteen trials involving 2,115 patients were included. Of these 13, eight measured "adherence to choice" and 10 measured "adherence to treatment." There was considerable heterogeneity in how adherence was measured, with studies varying in whether they considered baseline choice, follow-up choice, or neither, and whether they presented separate or aggregated adherence measures. No studies measuring "adherence to choice" reported significant differences between the decision aid and comparator, whereas four studies measuring adherence to treatment reported a statistically significant difference between the decision aid and comparator, with three favoring the decision aid arm. CONCLUSIONS:The adherence framework provided insight into important measurement factors. There remains considerable heterogeneity in measures of adherence which makes it difficult to draw conclusions.