Estimation of missed statin prescription use in an administrative claims dataset

Abstract

BACKGROUND: Nonadherence to statin medications is associated with increased risk of cardiovascular disease and poses a challenge to lipid management in patients who are at risk for atherosclerotic cardiovascular disease. Numerous studies have examined statin adherence based on administrative claims data; however, these data may underestimate statin use in patients who participate in generic drug discount programs or who have alternative coverage. OBJECTIVE: To estimate the proportion of patients with missing statin claims in a claims database and determine how missing claims affect commonly used utilization metrics. METHODS: This retrospective cohort study used pharmacy data from the PharMetrics Plus (P+) claims dataset linked to the IMS longitudinal pharmacy point-of-sale prescription database (LRx) from January 1, 2012, through December 31, 2014. Eligible patients were represented in the P+ and LRx datasets, had ≥1 claim for a statin (index claim) in either database, and had ≥ 24 months of continuous enrollment in P+. Patients were linked between P+ and LRx using a deterministic method. Duplicate claims between LRx and P+ were removed to produce a new dataset comprised of P+ claims augmented with LRx claims. Statin use was then compared between P+ and the augmented P+ dataset. Utilization metrics that were evaluated included percentage of patients with ≥ 1 missing statin claim over 12 months in P+; the number of patients misclassified as new users in P+; the number of patients misclassified as nonstatin users in P+; the change in 12-month medication possession ratio (MPR) and proportion of days covered (PDC) in P+; the comparison between P+ and LRx of classifications of statin treatment patterns (statin intensity and patients with treatment modifications); and the payment status for missing statin claims. RESULTS: Data from 965,785 patients with statin claims in P+ were analyzed (mean age 56.6 years; 57% male). In P+, 20.1% had ≥ 1 missing statin claim post-index; 13.7% were misclassified as nonstatin users; and 14.9% were misclassified as new statin users. MPR was higher in the augmented P+ dataset versus the P+ dataset alone for all patients (79.4% vs. 76.7%, P < 0.001) and new users (61.4% vs. 58.7%, P < 0.001). Similarly, mean PDC was higher in the P+ dataset augmented with LRx versus the P+ dataset alone for all patients (76.0% vs. 74.0%, P < 0.001) and new users (58.5% vs. 56.5%, P < 0.001). Most patients received moderate-intensity statins; few changes in dose, intensity, or discontinuation of statins were observed when the P+ dataset was augmented. The most common reasons for missing data were payment by an alternate third-party program (66.3%) and use of cash, coupon, or discount cards (18.7%). CONCLUSIONS: Augmenting commercial claims data with point-of-sale data provides a more accurate assessment of statin use than claims data alone.