ASSESSMENT OF A FOOD FREQUENCY QUESTIONNAIRE AS A SCREENING TOOL FOR LOW-FAT INTAKES

This study tested the ability of a self-administered food frequency qu estionnaire (FFQ) to identify women with low fat intakes. FFQs were co mpleted by 95 control participants of a dietary trial at a mean of 2.9 +/- 0.8 years post-randomization. Subjects were selected in approxima tely equal numbers from women who were low-fat eaters (less than or eq ual to 30% of energy from fat) and high-fat eaters (>30% of energy fro m fat). Percentage energy from fat derived from food records and FFQ w ere similar in both the low- and high-fat eaters. Percentage of energy from carbohydrate and total grams of carbohydrate (low-fat eaters onl y) were slightly higher measured by FFQ than by food records, and perc entage of energy from protein was slightly lower. The correlation betw een nutrient intake measured by FFQ and food records for the whole gro up was 0.74 for percentage of energy from fat, 0.50 for total fat, 0.5 9 for percentage of energy from carbohydrate, 0.43 for total carbohydr ate, 0.53 for percentage of energy from protein, 0.27 for total protei n, and 0.32 for energy intake. Correlations were slightly lower when t he low- and high-fat eaters were examined separately. The area under t he receiver operating characteristic (ROC) curve, 0.83, was significan tly above 0.5 (p much less than 0.001), indicating that the FFQ discri minated between low- and high-fat eaters significantly better than cha nce. The FFQ cutoff point of 30% of energy from fat had a true positiv e rate of 0.63 and false positive rate of 0.24. The use of this cutoff point for screening would result in the loss of 36% of potential subj ects and an estimated increase in baseline percentage of energy from f at intake of 2.3 percentage points. (C) Elsevier Science Inc. 1997.