title: Validation of a semi-quantitative food frequency questionnaire measuring dietary vitamin K intake in elderly people.
abstract: The study objective was to validate a semi-quantitative food frequency questionnaire (FFQ) specifically designed to measure dietary vitamin K intake. A 50-item FFQ was interviewer-administered and compared with data previously obtained from 5-day food records. Thirty-nine community-dwelling healthy men and women aged 65 to 85 years were recruited from the Montréal metropolitan area. Absolute and relative agreements between methods were assessed. Vitamin K intake measured by the vitamin K FFQ (mean+/-standard deviation; 222+/-186 microg/day) was significantly higher than that obtained by food records (135+/-153 microg/day; P<0.001). Bland-Altman analysis on log(10)-transformed data indicated that vitamin K intake from vitamin K FFQ was 2.26 times (95% confidence interval: 1.90 to 2.67) higher than food records, limits of agreement ranging from 0.80 to 6.35. However, correlation between methods was strong and highly significant (r=0.83; P<0.001). Cross-classification also showed that 72% of participants were correctly classified into thirds and only 8% were grossly miscategorized. Weighted kappa value (kappa=0.60) also indicated a good relative agreement. In light of these results, the vitamin K FFQ is a valid tool for ranking individuals according to their vitamin K intake. The poor absolute agreement likely results from the inability for food records to adequately measure the usual intake of episodically consumed foods, particularly those high in vitamin K. The vitamin K FFQ will be useful in large-scale, population-based research on vitamin K and disease as well as in clinical practice, especially that focusing on anticoagulant therapy.
authors: Centre de recherche, Institut universitaire de gériatrie de Montréal and Département de nutrition, Université de Montréal, Montréal, Canada.
authors: Nancy
authors: N
authors: Presse
authors: Bryna
authors: B
authors: Shatenstein
authors: Marie-Jeanne
authors: MJ
authors: Kergoat
authors: Guylaine
authors: G
authors: Ferland
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000933:Antifibrinolytic Agents / Q000008:administration & dosage*; D015930:Diet Records; D005260:Female; D015577:Geriatric Assessment; D006801:Humans; D008297:Male; D015596:Nutrition Assessment; D009751:Nutritional Requirements; D011792:Quebec; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D011795:Surveys and Questionnaires / Q000592:standards*; D014812:Vitamin K / Q000008:administration & dosage*; D014813:Vitamin K Deficiency / Q000175:diagnosis
chemical_list: D000933:Antifibrinolytic Agents; D014812:Vitamin K