ASSOCIATIONS OF RACE ETHNICITY, EDUCATION, AND DIETARY INTERVENTION WITH THE VALIDITY AND RELIABILITY OF A FOOD FREQUENCY QUESTIONNAIRE - THE WOMENS HEALTH TRIAL FEASIBILITY STUDY IN MINORITY POPULATIONS/

This report describes the associations of race/ethnicity and years of education with the validity, reliability, and bias of a self-administe red food frequency questionnaire (FFQ) designed to be sensitive to low -fat, regional, and ethnic dietary patterns. Data were from the Women' s Health Trial Feasibility Study in Minority Populations, a randomized clinical trial conducted between 1992 and 1994 to test the feasibilit y of a low-fat dietary intervention that targeted low-income, black, a nd Hispanic women. Of 1,015 participants eligible for these analysis, 28.1% were black, 16.2% were Hispanic, and 12.3% had not completed hig h school. The analyses focused on percentage of energy obtained from f at, and used 4-day food records as the criterion instrument. Validity at baseline, defined as the correlation between FFQs and food records, was lower among blacks than among whites (0.26 vs. 0.49; p < 0.001), did not differ between Hispanics and whites, and was lower among women with fewer years of education (0.19, 0.35, 0.39, and 0.42 for <12, 12 , 13-15, and greater than or equal to 16 years of education, respectiv ely; for trend, p < 0.05). Six months after randomization, validity in creased in most race/ethnicity and education subgroups, and difference s across groups became small and statistically nonsignificant. Validit y increased significantly among participants receiving the dietary int ervention, while increases among control women were somewhat smaller. Reliability, defined as the correlation between baseline and 6-month m easures among controls, was similar across racial/ethnic and education al groups. Bias at baseline, defined as the mean value from the FFQ mi nus the mean from the food record, was 4.6 percentage points of energy from fat; it was lowest among blacks (p < 0.01) and did not differ by years of education. These results suggest that special protocols whic h address participant training may be necessary when using self-admini stered FFQs in minority or poorly educated populations.