A Gap Analysis Approach to Assess Patient Persistence with Glaucoma Medication

Purpose To develop an alternative method for analysis of patient persistence with prescribed medications using the prostaglandin class of intraocular pressure (IOP)-lowering drugs as a model. Design A retrospective study of prescription refill patterns. Methods Patients with a pharmacy claim for a 2.5 ml bottle of latanoprost, travoprost, or bimatoprost between September 1, 2002 and December 31, 2002 were identified from a retail pharmacy database and were followed up for 12 months. Three separate analyses defined gaps in therapy as spans in excess of 45, 60, or 120 days without a refill for the same medication. Patients were categorized by the number of gaps in therapy and the cumulative length of gaps. A Kaplan-Meier analysis was conducted using a 120-day allowable refill period. Results For refill periods of 45, 60, and 120 days, 10.6%, 28.6%, and 77.5% of patients, respectively, had no gaps in therapy, and 32.6%, 53.4%, and 86.5%, respectively, had 30 days or fewer off therapy annually. According to the 45-day threshold analysis, 50.7% of patients had three or more gaps vs 18.5% in the 60-day analysis and none in the 120-day analysis. The Kaplan-Meier curve shows 88.6% and 76.1% of patients were persistent for 120 days and one year, respectively. Conclusions Compared with Kaplan-Meier survival curves, the gap analysis approach may better parallel clinical experience with patient persistence, in which patients stop and restart medications for a variety of reasons over time. This method also may help to identify avenues for investigation of lack of persistency among many patients.