Participants with chronic coronary disease (CCD) were randomized in the ISCHEMIA (International Study of Comparative Health Effectiveness With Medical and Invasive Approaches) to medical care following guidelines with or without angiography and revascularization. For a study, researchers sought to determine the relationship between nonadherence and outcomes related to health status. According to the study’s a priori premise, nonadherent patients would have a better health status if randomly assigned to invasive therapy; it compared the 12-month health status outcomes of adherent and nonadherent participants with CCD.

Using a modified 4-item Morisky-Green-Levine Adherence Scale, participants’ self-reported medication-taking behavior was evaluated randomly and categorized as adherent or non-adherent. The 7-item Seattle Angina Questionnaire (SAQ-7) summary score (SS), which runs from 0 to 100 (higher score = better), was used to evaluate 12-month health status. Bayesian proportional odds models, which included an interaction by the study arm, were used to assess the relationship between adherence and results (conservative vs. invasive).

About 1,245 (27.3%) of the 4,480 randomly chosen individuals were not adherent initially. Both the conservative (72.9±19.3 vs. 75.6±18.4) and the intrusive (71.0±19.8 vs. 74.2±18.7) arms of nonadherent subjects had lower baseline SAQ-7 SS scores. Adherence was linked to greater 12-month SAQ-7 SS in both treatment groups in adjusted analyses (mean difference in SAQ-7 SS with conservative therapy = 1.6 [95% credible interval: 0.3-2.9] vs. with invasive management = 1.9 [95% credible interval: 0.8-3.1]), with no treatment interaction.

More than 1 in 4 patients admitted to not taking their medications as prescribed, linked to lower health status at baseline and after a year of therapy using conservative and invasive methods. Therefore, regardless of the chosen treatment plan, strategies to increase drug adherence are required to enhance health status results in CCD.