Development of a multi-nutrient data quality evaluation system

The U.S. Department of Agriculture's (USDA) Nutrient Data Laboratory (NDL) has redesigned the software of the USDA Nutrient Databank to provide a system for data acquisition, compilation, and dissemination, and as part of this system has developed a module to facilitate the evaluation of analytical data quality. USDA's first data evaluation procedures were developed as a manual system to assess the quality of analytical data for iron, selenium and carotenoids in foods. These procedures have been modified and expanded for multi-nutrient data quality evaluation. The same five evaluation categories; sampling plan, number of samples, sample handling, analytical method and analytical quality control, from the original work have been maintained but the evaluation questions have been made more objective. The rating scales for each category have been changed from discrete steps to a more continuous scale. These ratings are combined to give a Quality Index (QI), and Confidence Code (CC) that is disseminated with the nutrient data to indicate the level of confidence in the value. The algorithm for combining ratings from the five categories was revised from earlier systems to avoid the possibility that the aggregation of several mediocre data points would together, merit the highest CC. (C) 2002 Published by Elsevier science Ltd.