Comparison of medication adherence and associated health care costs after introduction of pioglitazone treatment in African Americans versus all other races in patients with type 2 diabetes mellitus: A retrospective data analysis

Abstract

Objective:The aim of this study was to compare treatment adherence and health care costs in African Americans versus all other races (All Others) in patients with type 2 diabetes mellitus starting treatment with pioglitazone. Methods:In this retrospective cohort study, the North Carolina Medicaid database was used (query dates: July 1, 2000, to June 30, 2003). Using at least 1 code from the International Classification of Diseases, Ninth Revision, Clinical Modification for type 2 diabetes (250.xx) and 1 National Drug Code for antidiabetic medication, we identified a cohort of male and female patients aged ≥18 years with type 2 diabetes who maintained continuous Medicaid eligibility for the entire 36-month follow-up period. Race was categorized as African American and All Others (white, Asian, Native American, Pacific Islander, other) based on self-reported data collected at the time of Medicaid enrollment. Medication adherence was expressed as medication possession ratio (calculated as the number of days of antidiabetic prescription supply dispensed [eg, a 30-day supply] divided by the number of days between the first and last dispensation). Reimbursements made by Medicaid were used to calculate diabetes-related and total health care costs, which included medical and dental care, including costs for regular checkups, office visits, home health care, inpatient and outpatient care, long-term care facility care, and prescription drugs. To compare the differences in medication adherence and annual total and diabetes-related health care costs between African Americans and All Others, multivariate regression analysis was performed using only data from the year after (year 2) the year in which pioglitazone treatment was started (year 1). Results:Among the 1073 patients treated with pioglitazone (26.1% men; mean [SD] age, 49.5 [10.6] years; 50.2% African American; mean [SD] total health care costs in year 1, US $7906 [$12,256]; year 2, $9546 [$14,861]), African Americans had significantly higher adherence (62%) to pioglitazone treatment compared with All Others (57%) (P < 0.05) on unadjusted analysis. However, no significant differences in rates of adherence to the medication were found between African Americans and All Others on multivariate regression analysis. African American race was not found to be an independent predictor of increased or decreased annual total health care costs in this population. Significant reductions in total health care costs (2% for every 10% increase in adherence; P < 0.001) and diabetes-related costs (4% for every 10% increase in adherence; P < 0.01) with increased adherence were found. Conclusions:On multivariate analysis, this study found no significant differences in treatment adherence between African Americans versus all other races in this population of diabetic patients enrolled in a Medicaid program (query dates: July 1, 2000, to June 30, 2003). A higher adherence rate was associated with significantly lower diabetes-related and total health care costs in this population.