Relative validity and reproducibility of a 14-item semi-quantitative food frequency questionnaire for cardiovascular prevention.

BACKGROUND: Dietary habits play a major role in cardiovascular disease risk but few simple nutrition assessment tools are available for clinical practice. We developed a 14-item food frequency questionnaire to evaluate dietary patterns in relation with coronary risk in a French population. DESIGN AND METHODS: This food frequency questionnaire gave different scores of intake: saturated fatty acids (six questions), mono-unsaturated fatty acids, Omega-3 and Omega-6/Omega-3 polyunsaturated fatty acids (five questions), and fruits and vegetables (three questions). Validity was assessed against a 7-day dietary history (n = 49 subjects) and against biomarkers (n = 181). The food frequency questionnaire was also administered twice with an interval of 15 days to evaluate its reproducibility (n = 20). RESULTS: Validity against dietary history was assessed with Spearman correlation coefficients which ranged from 0.47 (fruits and vegetables) to 0.63 (polyunsaturated fatty acids/saturated fatty acids) (all P < 0.05), with a mean value of 0.54. On average, 39% of the subjects were classified in the same quartile with the food frequency questionnaire and the dietary history and 84% in the same or adjacent quartile. Biomarker-based validity using Spearman correlation coefficients varied from 0.21 (saturated fatty acids) to 0.53 (Omega-3 polyunsaturated fatty acids) (all P < 0.05), with a mean value of 0.35. On average, 37% of the participants were classified in the same quartile with the food frequency questionnaire and the corresponding biomarkers and 73% in the same or adjacent quartile. Reproducibility assessed by the intraclass correlation coefficient ranged from 0.71 (mono-unsaturated fatty acids) to 0.93 (global score), with a mean value of 0.81. CONCLUSION: We validated a short food frequency questionnaire for dietary pattern assessment in coronary prevention