Health outcomes and economic impact of therapy conversion to a biphasic insulin analog pen among privately insured patients with type 2 diabetes mellitus

Study Objective. To evaluate claims-related treatment adherence, health care resource utilization, and associated costs of therapy conversion from an insulin vial and syringe to a premixed biphasic insulin analog pen device among privately insured patients with type 2 diabetes mellitus. Design. Retrospective, longitudinal, intrapatient (before and after) analysis. Data Source. PharMetrics database of medical and pharmaceutical claims from 57 commercial health plans across the United States. Patients. Four hundred eighty-six adult patients with a confirmed diagnosis of type 2 diabetes who converted from an insulin analog vial and syringe (233 patients) or a human insulin vial and syringe (253 patients) to a biphasic insulin analog pen device between July 1, 2001 and December 3 1, 2002. Measurements and Main Results. All patients had no previous use of the pen device. Primary end points were medication possession ratio (MPR), a measure of adherence; hypoglycemic events; associations between treatment adherence and hypoglycemic events, and adherence and all-cause health care costs; and all-cause-attributable, hypoglycemia-attributable, and other diabetes-attributable costs. After conversion, MPR increased significantly from 59% to 68% (p<0.01). A significant decrease in the likelihood of experiencing a hypoglycemic event was, also observed after conversion (odds ratio [OR] 0.40, 95% confidence interval [CI] 0.27-0.61, p<0.05), with hypoglycemic occurrences reduced nearly two thirds among subjects with optimal adherence indicated by an MPR of 80% or greater (incidence rate ratio 0.36, 95% Cl 0.11-0.76, p<0.05). Significant decreases in hypoglycemia-attributable emergency department visits (OR 0.36, 95% CI 0.16-0.84, p<0.05) and physician visits (OR 0.39, 95% CI 0.20-0.77, p<0.05) were observed. Total mean all-cause annual treatment costs were reduced by $1748/patient (p<0.01), hypoglycemia-attributable costs were reduced by $908/patient (p<0.01), and other diabetes-attributable costs were reduced by $643/patient (p<0.01). Patients with an MPR of 80% or greater were associated with significant reductions in all-cause health care costs (OR 0.55, 95% CI 0.31-0.80, p<0.05). Conclusion. Privately insured patients with type 2 diabetes may exhibit considerable improvements in clinical and economic outcornes after insulin therapy conversion from vial and syringe to a premixed biphasic insulin analog pen device.