Comparison of the 60-and 100-item NCI-block questionnaires with validationdata

Large epidemiological studies often require short food frequency questionna ires (FFQ) to minimize the respondent burden or to control for confounding from dietary factors. In this analysis, we compared the extensively used Na tional Cancer institute-Block 60- and 100-item FFQs with one another and wi th usual intake as estimated from 12 clays of validation data. The analysis focused on nutrients from different aspects of the diet, including energy, fat, saturated fat, p-carotene, dietary fiber, and vitamin C. By use of an errors-in-variables analysis, the correlations of usual intake with the tw o types of FFQs for these nutrients were not different. Attenuation coeffic ients, a measure of misclassification error, far both FFQs were of similar magnitude and indicated that substantial attenuation of logistic regression coefficients would result from either FFQ. Our results confirm previous an alyses describing the validity and utility of the 60-item FFQ (Epidemiology 1, 58-64, 1990) and indicate that it is essentially equivalent to the 100- item FFQ for epidemiological analyses of major nutrients.