Quantification of missing prescriptions in commercial claims databases: results of a cohort study.

PURPOSE: This study aims to quantify the magnitude of missed dispensings in commercial claims databases. METHODS: A retrospective cohort study has been used linking PharMetrics, a commercial claims database, to a prescription database (LRx) that captures pharmacy dispensings independently of payment method, including cash transactions. We included adults with dispensings for opioids, diuretics, antiplatelet medications, or anticoagulants. To determine the degree of capture of dispensings, we calculated the number of subjects with the following: (1) same number of dispensings in both databases; (2) at least one dispensing, but not all dispensings, missed in PharMetrics; and (3) all dispensings missing in PharMetrics. Similar analyses were conducted using dispensings as the unit of analysis. To assess whether a dispensing in LRx was in PharMetrics, the dispensing in PharMetrics had to be for the same medication class and within ±7 days in LRx. RESULTS: A total of 1 426 498 subjects were included. Overall, 68% of subjects had the same number of dispensings in both databases. In 13% of subjects, PharMetrics identified ≥1 dispensing but also missed ≥1 dispensing. In 19% of the subjects, PharMetrics missed all the dispensings. Taking dispensings as the unit of analysis, 25% of the dispensings present in LRx were not captured in PharMetrics. These patterns were similar across all four classes of medications. Of the dispensings missing in PharMetrics, 48% involved a subject who had >1 health insurance plan. CONCLUSIONS: Commercial claims databases provide an incomplete picture of all prescriptions dispensed to patients. The lack of capture goes beyond cash transactions and potentially introduces substantial misclassification bias. © 2017 The Authors. Pharmacoepidemiology & Drug Safety Published by John Wiley & Sons Ltd.

Drug therapies for Parkinson's disease: A database analysis of patient compliance and persistence.

BACKGROUND: Evaluating medication adherence in Parkinson's disease (PD) is important to avoid erroneously attributing suboptimal patient outcomes from poor compliance to disease progression or adverse responses to medications. OBJECTIVE: This study of patients with PD who were new to PD drug therapy examined patient compliance and persistence, by drug, to provide a comprehensive investigation of medication-taking behavior in PD. METHODS: A retrospective analysis of patients receiving a new PD drug between March 1 and May 31, 2007, was conducted, using the IMS Health longitudinal prescription database, which contains ∼50% of all retail prescriptions and <150 million patients in the United States. Patients were considered to have received a new PD drug if they initiated PD therapy for the first time, added adjunctive PD therapy, or switched one PD drug for another. Patients were categorized as naive to PD therapy (NT) or having prior PD therapy (PT), which included adjunctive use and switches. The PD medications evaluated were rasagiline, levodopa/carbidopa, levodopa/carbidopa/entacapone, the catechol-O-methyltransferase (COMT) inhibitors (entacapone and tolcapone), pramipexole, ropinirole, and selegiline. The study consisted of a 12-month look-back period (during which patients were required to be active in the database), a 3-month selection period (during which patients received their first prescription), and a 12-month observation period. Compliance was measured using the medication possession ratio (MPR; defined as the number of days' supply of medication divided by the number of available days of therapy, from first dispense date in the selection period to last dispense date in the observation period); noncompliance was defined as an MPR ≤80%. Persistence was measured as the duration (days) of uninterrupted therapy. RESULTS: A total of 29,682 patients with PD (19,673 NT, 10,009 PT) received a new PD drug and were analyzed. Of the 19,510 patients included in the compliance analysis, 10,438 (53.5%) had compliance rates >80% and 9072 (46.5%) were noncompliant. For all patients (NT and PT), compliance rates were significantly higher for patients taking rasagiline than for those taking other PD medications (all P < 0.001). For all patients, the highest mean number of persistent days of treatment (147.5) was reported for rasagiline, followed by levodopa/carbidopa/ entacapone (146.9); persistence for both of these drugs was significantly higher than that for the comparator medications (rasagiline vs levodopa/carbidopa, P = 0.002; rasagiline vs pramipexole, P = 0.003; rasagiline vs COMT inhibitors, ropinirole, and selegiline, all P < 0.001; levodopa/carbidopa/entacapone vs levodopa/carbidopa, P = 0.005; levodopa/carbidopa/entacapone vs pramipexole, P = 0.006; levodopa/carbidopa/entacapone vs COMT inhibitors, ropinirole, and selegiline, all P < 0.001). Almost half of the patients (13,103; 44.1%) remained on their PD medication ≥90 days. CONCLUSIONS: This study found a differential compliance and persistence across PD drug therapies. The compliance rate for rasagiline was significantly higher than that for all of the other PD medications. In addition, rasagiline and levodopa/carbidopa/entacapone were associated with significantly higher persistence rates than were the other PD medications.