Cooperative studies in health services research in the Department of Veterans Affairs.

The Department of Veterans Affairs, through its Cooperative Studies Program, has a long history of conducting large-scale, multihospital biomedical clinical trials. The agency's Health Services Research and Development Service, although newer, has a distinguished record of mainly single-site research into the organization, delivery, and financing of health services. In 1990, a joint program was initiated to conduct multicenter studies in health services research. This article describes the studies developed in the new program and the research design issues encountered in planning them. Identification of the patient population, specification and measurement of the intervention, and description of the control group, as well as attention to the unit of randomization and analysis, outcome variables and choice of effect size, data quality, and ethical considerations are among the important issues related to the design of these studies and future studies in health services.