Presse N, Shatenstein B, Kergoat MJ, Ferland G. Validation of a semi-quantitative food frequency questionnaire measuring dietary vitamin K intake in elderly people.
ACTA ACUST UNITED AC 2009;
109:1251-5. [PMID:
19559145 DOI:
10.1016/j.jada.2009.04.019]
[Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2008] [Accepted: 12/02/2008] [Indexed: 01/07/2023]
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.
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