Designing a quality assurance system for dietary data in a multicenter clinical trial: Women's Intervention Nutrition Study.

Reliable dietary intake data are essential for determining outcomes in nutrition-related clinical trials. Nevertheless, systems for quality assurance of dietary intake data are often slighted in the design of such trials and not incorporated or monitored as the trials continue. The Women's Intervention Nutrition Study (WINS), a multicenter clinical trial investigating the effect of reduction of dietary fat intake together with adjuvant systemic therapy on recurrence rates in and survival of postmenopausal women with early stage, surgically treated, breast cancer, has developed a quality assurance system to minimize errors and to produce data that are complete and reliable. The system involves development of standardized procedures for data collection, a quality control program to evaluate the data collected, and continual monitoring and reevaluation. The WINS system is offered as a model for studies collecting dietary intake data, no matter how simple or complex the trial design.