Accuracy of Patient-reported Adherence to Glaucoma Medications on a Visual Analog Scale Compared with Electronic Monitors

Purpose Glaucoma medications can improve clinical outcomes when patients adhere to their medication regimen. Providers often ask patients with glaucoma to self-report their adherence, but the accuracy of self-reporting has received little scientific attention. The purpose of this article was to compare a self-reported medication adherence measure with adherence data collected from Medication Event Monitoring Systems (MEMS) electronic monitors. An additional goal was to identify which patient characteristics were associated with overreporting adherence on the self-reported measure. Methods English-speaking adult patients with glaucoma were recruited from 6 ophthalmology practices for this observational cohort study. Patients were interviewed after their initial visit and were given MEMS contains, which recorded adherence over a 60-day period. MEMS percent adherence measured the percentage of the prescribed number of doses taken. MEMS-measured timing adherence assessed the percent doses taken on time. Patients self-reported adherence to their glaucoma medications on a visual analog scale (VAS) ∼60 days after the baseline visit. Bivariate analyses and logistic regressions were used to analyze the data. Self-reported medication adherence on the VAS was plotted against MEMS adherence to illustrate the discrepancy between self-reported and electronically monitored adherence. Findings The analyses included 240 patients who returned their MEMS containers and self-reported medication adherence at the 60-day follow-up visit. Compared with MEMS-measured percent adherence, 31% of patients (n = 75) overestimated their adherence on the VAS. Compared with MEMS-measured timing adherence, 74% (n = 177) of patients overestimated their adherence. For the MEMS-measured percent adherence, logistic regression revealed that patients who were newly prescribed glaucoma medications were significantly more likely to overreport adherence on the VAS (odds ratio, 3.07 [95% CI, 1.22-7.75]). For the MEMS-measured timing adherence, being male (χ² test, 6.78; P = 0.009) and being prescribed glaucoma medications dosed multiple times daily (χ² test, 4.02; P = 0.045) were significantly associated with patients overreporting adherence. However, only male sex remained a significant predictor of overreporting adherence in the logistic regression (odds ratio, 4.05 [95% CI, 1.73-9.47]). Implications Many patients with glaucoma, especially those newly diagnosed, overestimated their medication adherence. Because patients were likely to overreport the percent doses taken and timing adherence, providers may want to ask patients additional questions about when they take their glaucoma medications to potentially detect issues with taking these medications on time.