Validation of a food frequency questionnaire in Spanish patients with familial hypercholesterolaemia.

BACKGROUND AND AIMS: The aim of this study is to validate a semi-quantitative Food Frequency Questionnaire (FFQ) used for general population in Spain, in patients with familial hypercholesterolaemia (FH). SUBJECTS AND METHODS: Subjects with genetic diagnosis of FH were randomly selected from the Spanish FH Registry. They completed an FFQ based in 113 food items at inclusion (FFQ1) and after 1 year (FFQ2), and a 3-day dietary records (DR) every 3 months. Detailed instruction about how to register foods and beverages was given by a trained nutritionist. Each DR and FFQ was systematically coded, and the daily nutrients intake in absolute, percentage and nutrient density terms were estimated using a software system based on food composition tables. Pearson correlation coefficient was calculated with correction-repeated measurements to assess the reproducibility of both FFQ and the four 3-day DRs, as well as the validity of FFQ comparing to the mean of 3 days' DR. RESULTS: A total of 112 subjects (58 females and 54 males, aged 43 ± 16 years) finished the study. There were no differences between FFQ1, FFQ2 and mean FFQ (FFQa) in mean absolute and percentage values of selected daily nutrients' intake. Comparison between FFQ1, FFQ2, FFQa and the mean of four 3-day DRs was statistically significant in all absolute values, but not in percentage or nutrient density terms. Corrected Pearson correlation coefficient ranged from 0.470 to 0.952 for mean values of all nutrients, except alcohol. CONCLUSION: This study demonstrated that FFQ is a reliable tool to assess the dietary pattern in FH patients.