Direct health care costs for treatment of diabetes mellitus and hypertension in an IPA-group-model HMO.

The differences in direct health care costs and use between HMO enrollees with both diabetes mellitus and hypertension and enrollees with either disease alone were studied. Two years' worth of medical and pharmacy claims data from a hybrid (independent practice association and group)-model HMO were evaluated. Diagnoses were determined from medical claims data and cross-referenced with prescription information from pharmacy claims data. Aggregate costs associated with each disease, including pharmacy costs, costs of physician office visits, and laboratory costs, were compiled. Comparisons were made of all costs (any cost incurred by the health plan for the member, regardless of disease) and disease-specific costs. The frequency of comorbid conditions was identified. A total of 6195 patients (670 with diabetes and hypertension, 1756 with diabetes alone, and 3769 with hypertension alone) were assessed. Patients with both diseases incurred much higher costs per year than patients with diabetes or hypertension alone (mean costs, $13,446, $8,493, and $8,424, respectively). Hospitalization costs contributed the greatest amount to total costs, while emergency room costs contributed the least. Disease-specific costs for diabetes and hypertension represented less than one quarter of total health care costs per patient. Average disease-specific costs were highest for patients with both diseases ($2,955), followed by costs for patients with hypertension alone ($1,803) and patients with diabetes alone ($689). The percentage spent on prescriptions was much higher for disease-specific costs than for total costs. The three most common comorbid conditions were dyslipidemia, coronary artery disease, and chronic obstructive pulmonary disease, with the frequency of cerebrovascular disease and myocardial infarction more than double in patients with diabetes and hypertension compared with patients with either disease alone. The cost of care for a patient with both diabetes and hypertension, although not double that for a patient with diabetes or hypertension alone, was higher than the cost of treating either disease.