Quality control in the Multiple Risk Factor Intervention Trial Nutrition Modality.

One of the principal objectives of the MRFIT was to teach and motivate participants assigned to the SI group to adhere to a fat-controlled dietary regimen over the course of the trial. The magnitude of the trial (with more than 12,000 participants, half of them assigned to the SI protocol, to be followed for at least 6 years in 22 separate centers) presented new challenges for maintenance of quality control over a nutrition intervention program. Collection of data to monitor changes in dietary intake over time in SI and UC groups, as well as information to assess dietary adherence levels in SI participants also presented large-scale challenges in maintenance of quality control. The MRFIT formulated many of its initial nutrition intervention and data collection decisions based on experience of the earlier National Diet Heart Study (NDHS). In order to avoid coding 7-day dietary records by local clinic nutritionists (as in NDHS), the trial opted for collection of 24-hour dietary recalls that were coded centrally at the Nutrition Coding Center. It necessitated extra attention to training and certification of clinic nutritionist-interviewers to be certain that NCC coders had sufficiently precise information about all foods entered on dietary recall forms. Since dietary intake data were collected over a time span of approximately 10 years, procedures for updating the food composition database and coding rules were a necessity. Continuing attention to training and monitoring of performance of clinic nutritionist-interviewers also was important. The MRFIT nutrition intervention program was designed with the need for interclinic comparability of intervention techniques in mind. This required not only development of study-wide nutrition intervention materials, but also necessitated ongoing attention to staff training and monitoring procedures in order to ensure intercenter comparability of efforts. The success of the nutrition intervention modality depended upon the continuing efforts of the nutrition counselors not only to achieve dietary adherence but also to monitor levels of dietary adherence over time. The NDHS experience served as a springboard for designing the MRFIT nutrition intervention and data collection procedures. It is hoped that techniques for maintaining and monitoring quality control over the MRFIT nutrition modality as outlined in this chapter may prove useful to future planners.