Accurate methods of identifying patients with suboptimal adherence to cardiometabolic medications are needed, and each approach has benefits and tradeoffs.

We used data from a large trial of patients with poorly controlled cardiometabolic disease and evidence of medication non-adherence measured using pharmacy claims data whose adherence was subsequently assessed during a telephone consultation with a clinical pharmacist. We then evaluated if the pharmacist assessment agreed with the non-adherence measured using claims. When pharmacist and claims assessments disagreed, we identified reasons why claims were insufficient and used multivariable modified Poisson regression to identify patient characteristics associated with disagreement.

Of 1,069 patients identified as non-adherent using claims (proportion of days covered [PDC] <80%), 646 (60.4%) were confirmed as non-adherent on pharmacist interview. For the 423 patients (39.6%) where the interview disagreed with the claims, the most common reasons were paying cash or using an alternate insurance (36.6%), medication discontinuation or regimen change (32.8%), and recently becoming adherent (26.7%). Compared to patients whose claims and interview both showed non-adherence, patients whose interview disagreed with claims were less likely to miss outpatient office visits (RR:0.91, 95%CI:0.85-0.97) and more likely to have a baseline PDC above the median (RR:1.35, 95%CI:1.10-1.64).

Among patients identified as non-adherent by claims, 39.6% were observed to be adherent when assessed during pharmacist consultation. This discrepancy was largely driven by paying out-of-pocket, using alternative insurance, or medication discontinuation or change. These findings have important implications for using pharmacy claims to identify and intervene upon medication non-adherence.