Medical Costs of Patients with Type 2 Diabetes in a Single Payer System: A Classification and Regression Tree Analysis

Background and objectives Many studies and systematic reviews have estimated the healthcare costs of diabetes using a cost-of-illness approach. However, in the studies based on this approach patients’ heterogeneity is rarely taken into account. The aim of this study is to stratify patients with type-2 diabetes into homogeneous cost groups based on demographic and clinical characteristics. Methods We conducted a retrospective cost of illness study by linking individual data on health services utilization retrieved from the administrative databases of Emilia-Romagna Region (Italy). Direct medical costs (either all-cause or diabetes-related) were calculated from the perspective of regional health service, using tariffs for hospitalizations and outpatient services and the unit costs of prescriptions for drugs. The determinants of costs identified in a generalized linear regression model were used to characterize subgroups of patients with homogeneous costs in a classification and regression tree analysis. Results The study population consists of a cohort of 101,334 patients with type 2 diabetes, followed up for 1 year, with a mean age of 70.9 years. Age, gender, complications, comorbidities and living area accounted significantly for cost variability. The classification tree identified 10 patient subgroups with different costs, ranging from a median of € 483 to € 39,578. The 2 subgroups with highest costs comprised dialysis patients and the largest subgroup (57.9%) comprised patients aged ≥65 years without renal, cardiovascular and cerebrovascular complications. Conclusions Patients’ classification into homogeneous cost subgroups can be used to improve the management and budget allocation for patients with type 2 diabetes.