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 w ith both diabetes mellitus and hypertension and enrollees with either disea se alone were studied. Two years' worth of medical and pharmacy claims data from a hybrid (indepen dent practice association and group)-model HMO were evaluated. Diagnoses we re determined from medical claims data and cross-referenced with prescripti on information from pharmacy claims data. Aggregate costs associated with e ach disease, including pharmacy costs, costs of physician office visits, an d 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 identifie d. A total of 6195 patients (670 with diabetes and hypertension, 1756 with dia betes alone, and 3769 with hyper tension alone) were assessed. Patients wit h both diseases incurred much higher costs per year than patients with diab etes or hypertension alone (mean costs, $13,446, $8,493, and $8,424, respec tively). Hospitalization costs contributed the greatest amount to total cos ts, while emergency room costs contributed the least. Disease-specific cost s 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 wi th hypertension alone ($1,803) and patients with diabetes alone ($689). The percentage spent on prescriptions was much higher for disease-specific cos ts than for total costs. The three most common comorbid conditions were dys lipidemia, coronary artery disease, and chronic obstructive pulmonary disea se, 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, althoug h not double that for a patient with diabetes or hypertension alone, was hi gher than the cost of treating either disease.