Treatment Persistence among Insulin Glargine Users

San Francisco—For insulin-dependent patients with type 2 diabetes mellitus (T2DM), treatment persistence may be critical in maintaining glycemic control. Poor treatment and adherence to treatment plan is associated with poor clinical outcomes, increased healthcare utilization, and increased cost. There have been few studies of the factors that predict patient persistence with treatment.

The objectives of this study, reported at an AMCP poster session, were to evaluate persistence of treatment among insulin glargine users who injected via vial/syringe or disposable pen, using healthcare plan claims data, and to identify factors that predicted persistence with treatment. The poster was titled An Empirical Approach to Measure and Predict Treatment Persistence among Insulin Glargine-Treated Patients with Type 2 Diabetes.

This retrospective database analysis utilized data taken from 2 claims databases (Thomas Reuters MarketScan^® and IMPACT). To be eligible for inclusion, patients had to have been diagnosed with T2DM and had to have at least 2 vial insulin glargine prescriptions during baseline. They had to have been enrolled in their health insurance plans continuously for 6 months before switching from vial to pen or had to continue on vial for the duration of the study.

Three distinct populations were studied: a nonelderly population (≥18 to <65 years of age) from the 2006-2010 MarketScan database; an elderly (≥65 years of age) population from the 2006-2010 MarketScan database; and a population (≥18 years) from the IMPACT database from 2006 to 2010.

Treatment adherence was measured by the adjusted medication possession ratio (MPR), calculated as the number of days of drug supply during baseline or follow-up period divided by the total number of days in the period. This was adjusted by multiplying the MPR by the average number of days between prescription refills divided by the average days of drug supply. Daily average consumption of insulin (DACON) was measured over the 6-month baseline and 1-year follow-up in units (IU) per day.

A total of 8984 matched patients were included in the analysis. The nonelderly MarketScan matched cohorts had 2891 patients; the elderly MarketScan cohorts contained 988 patients, and the IMPACT cohorts contained 603 patients.

On bivariate analysis, during the 1-year follow-up period, persistence was significantly higher for those who switched from vial to pen use than for those who stayed with vials in all 3 cohorts (MarketScan nonelderly, 70.0% vs 55.6%, P<.0001; MarketScan elderly, 65.3% vs 56.8%, P<.0001; IMPACT, 65.3% vs 49.8%, P<.0001). The number of persistent days during follow-up was significantly higher for the pen switcher cohort compared with the vial continuers in all 3 cohorts (MarketScan nonelderly, 313 vs 278 days, P<.0001; MarketScan elderly, 304 vs 282 days, P<.0001; IMPACT, 300 vs 264 days, P<.0001). DACON was similar for both cohorts in all 3 populations.

On multivariate analysis, logistic regression identified baseline factors that predicted 1-year treatment persistence in each of the 3 populations. In all populations, switching to pen predicted persistence (MarketScan nonelderly, OR 1.95, 95% confidence interval [CI] 1.72-2.19, P<.0001; MarketScan elderly, OR 1.44, 95% CI 1.19-1.76, P<.0003; IMPACT, OR 2.19, 95% CI, 1.70-2.82, P<.0001). Higher DACON at baseline predicted persistence in all 3 populations (MarketScan nonelderly, OR 1.02, 95% CI 1.01-1.02, P<.0001; MarketScan elderly, OR 1.01, 95% CI 1.01-1.02, P<.0001; IMPACT OR 1.02, 95% CI 1.01-1.03, P<.0001).

Higher adjusted MPR at baseline predicted persistence in the MarketScan nonelderly population and the IMPACT population. In the MarketScan nonelderly and the IMPACT populations, diagnosis of mental illness was associated with a lower persistence rate. In both MarketScan populations, a visit to an endocrinologist was associated with lower persistence. Disposable pen use predicted persistence in both MarketScan populations.

Across all 3 populations, the factors predicting a longer time to discontinuation were similar to those predicting persistence. Time to discontinuation was longer among pen switchers, those with higher baseline DACON, and those who had higher adherence rates at baseline as measured by adjusted MPR.

This study was supported by sanofi-aventis US.