Race-specific validation of food intake obtained from a comprehensive FFQ: the Adventist Health Study-2

Objective: To assess race-specific validity of food and food group intakes measured using an FFQ. Design: Calibration study participants were randomly selected from the Adventist Health Study-2 (AHS-2) cohort by church, and then by subject-within-church. Intakes of forty-seven foods and food groups were assessed using an FFQ and then compared with intake estimates measured using six 24 h dietary recalls (24HDR). We used two approaches to assess the validity of the questionnaire: (i) cross-classification by quartile and (ii) de-attenuated correlation coefficients. Setting: Seventh-day Adventist church members geographically spread throughout the USA and Canada. Subjects: Members of the AHS-2 calibration study (550 whites and 461 blacks). Results: The proportion of participants with exact quartile agreement in the FFQ and 24HDR averaged 46% (range: 29-87%) in whites and 44% (range: 25-88%) in blacks. The proportion of quartile gross misclassification ranged from 1% to 11% in whites and from 1 % to 15 % in blacks. De-attenuated validity correlations averaged 0.59 in whites and 0.48 in blacks. Of the forty-seven foods and food groups, fortythree in whites and thirty-three in blacks had validity correlations >0.4. Conclusions: The AHS-2 questionnaire has good validity for most foods in both races; however, validity correlations tend to be higher in whites than in blacks.