The study design, baseline patient characteristics, and outcome measures from the Managed Care Outcomes Project are discussed, and correlates of resource utilization and patient severity of illness described. The Managed Care Outcomes Project was an observational, cross-sectional, longitudinal study of 12,997 patients, eligible by having one or more of five diseases (hypertension, otitis media, arthritis, ulcers, and asthma) in a managed care setting. The data sources were six health maintenance organizations from six states, three in the eastern and three in the western United States. Between 1,876 and 2,663 patients at each health maintenance organization were studied. For each disease, there were between 1,309 and 3,938 patients, for a total of 12,997 patients across all diseases. Data on the disease-specific severity of illness were collected at each visit. Resource utilization included more than 99,000 office visits, 480 emergency department visits, 1,000 hospitalizations, and 240,000 prescriptions.

The study found that significant differences in resource utilization and severity of illness exist across age categories, disease groups, and organization characteristics. The results identify important differences in patient mix, diseases, and organization structural factors and cost-containment methods that must be considered when examining outcomes of care.