A gap analysis approach may be preferable to Kaplan-Meier survival curves for analysing patient persistence with prescribed medications.
A gap analysis approach may be preferable to Kaplan-Meier survival curves for analysing patient persistence with prescribed medications, according to a report published in the August issue of the American Journal of Ophthalmology.
Paul P. Lee and colleagues from the Eye Center at Duke University, North Carolina, USA conducted a retrospective study of prescription refill patterns. Patients with prescriptions for 2.5 ml bottles of latanoprost, travoprost and bimatoprost 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 categorised 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.
The results showed that, 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 that 32.6%, 53.4% and 86.5%, respectively, had 30 days or fewer off therapy in a 12-month period. According to the 45-day threshold analysis, 50.7% of subjects had three or more gaps versus 18.5% in the 60-day analysis and none in the 120-day analysis. The Kaplain-Meier curve demonstrated that 88.6% and 76.1% of subjects were persistent for 120 days and one year, respectively.
According to the researchers, it would appear that a gap analysis approach to analysing patient compliance is more accurate than using Kaplan-Meier survival curves.