Abstract
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, forty-three 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.