Accuracy of prescription claims data in identifying truly nonadherent patients

BACKGROUND: Administrative claims data are increasingly used to identify nonadherent patients. This necessitates a comprehensive review and assessment of their accuracy in identifying nonadherent patients. OBJECTIVES: To (a) compare administrative claims-based measures of adherence with nonadherence verified by patient interview; (b) determine if and to what extent patients classified as nonadherent based on prescription claims differ from patients classified as nonadherent based on interventions designed to gather multiple types of medication lists to compare against the prescription fill history; and (c) assess the various patientreported reasons for nonadherence. METHODS: A cross-sectional study was used to identify patients from the Southern Piedmont Community Care Network of North Carolina who were enrolled with Medicaid between January 1, 2012, and May 31, 2013, and were using prescription medications for 1 or more chronic conditions. Patients with more than a 30-day gap in refill history were identified using prescription claims and were interviewed by pharmacists to assess the reasons for nonadherence. Based on the patient-reported reasons for a gap in refill, patients were classified as interview-verified nonadherent patients or interview-verified adherent patients. The positive predictive value of prescription claims in identifying nonadherent patients was calculated, and descriptive statistics were reported. Characteristics of interview-verified nonadherent patients were compared with adherent patients using t-tests and chi-square statistics. RESULTS: 1,425 patients representing 2,936 patient-class of medication combinations were included in the final analysis. 824 (28.07%) of the 2,936 records that were flagged as nonadherent using claims analysis were confirmed as adherent during patient interviews. The positive predictive value of claims records in identifying nonadherent patients was 0.72. The 2 most common reasons for patients to be misclassified as nonadherent in claims data following self-report were discontinuation of medication on prescribers' directions (21.93%) and having an alternate channel for receiving the medication (6.13%). Among interview-verified nonadherent patients, side effects, patient beliefs, education, and socioeconomic barriers were the most common patient-reported reasons for gaps in refill. CONCLUSIONS: Prescription claims may underestimate adherence in patients. When interviewed directly by a pharmacist, most patients reported discontinuation of medication as per prescribers' directions. To determine the overall validity of prescription claims data, further analysis is required to assess its accuracy in identifying truly nonadherent patients among those who are identified as nonadherent by claims data.