Validation of a diet history questionnaire for use with Costa Rican adults.

Objective: To validate a diet history questionnaire (DHQ) using a weighed food record (WFR) as the standard method in the estimation of food consumption and nutrient intake in a group of adults.

Design: WFR: all foods consumed by subjects during 7 consecutive days were weighed and recorded by nutrition students. Two DHQ interviews were carried out on days 1 (first diet history questionnaire, DHQ1) and 28 (second diet history questionnaire, DHQ2).

Setting: Costa Rica.

Subjects: Sixty adults: 30 men and 30 women; 30 living in urban and 30 in rural areas.

Results: In comparison to the WFR, the DHQ1 gave statistically significant higher estimates of the mean intake of 19 nutrients for men and of three nutrients for women. The uncorrected correlation coefficients for nutrient intake according to both methods ranged from 0.40 to 0.83 for males and from 0.22 to 0.62 for females. Percentage of subjects classified in the same quartiles of nutrient intake according to each method ranged from 33.3% to 63.3% for males and from 23.3% to 53.3% for females. Misclassification in extreme quartiles ranged from 0% to 13.3% for both sexes. The mean food group consumption, according to the DHQ1, when compared with the WFR, gave statistically significant differences for three of the 18 food groups for men and for two groups in the case of women. The two applications of the DHQ gave similar results.

Conclusion: Validation of a DHQ using a WFR as the standard method gave results that compare favourably with those reported by other authors. This study found important differences in the response of men and women to the DHQ: among men, the estimates of mean nutrient intake from DHQ1 were significantly greater than those of the WFR, while in the case of women, the mean nutrient intake estimates from both methods were not significantly different. There was a higher degree of correlation between the DHQ1 and the WFR mean nutrient intakes among men than among women. The DHQ showed good reproducibility.