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 31, 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% CI 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 outcomes after insulin therapy conversion from vial and syringe to a premixed biphasic insulin analog pen device.