Validation and reproducibility of a novel flavonoid food frequency dietary assessment tool (Flav-Q) against multiple 24-h recalls across 12 months

Abstract Purpose Measurement of dietary flavonoid intake requires a reliable tool. This study validated and evaluated the reproducibility of a 23-item shortened flavonoid food frequency questionnaire (FLAV-Q), derived from the 96-item Kent κ = 0.45, p < 0.001), flavan-3-ols ( r = 0.72, p < 0.001; κ = 0.53, p < 0.001), flavonols ( r = 0.55, p < 0.001; κ = 0.40, p < 0.001), flavanones ( r = 0.50, p < 0.001; κ = 0.30, p = 0.007) and fair but non-significant agreement for anthocyanins ( r = 0.38, p < 0.001; κ = 0.15, p = 0.18) and flavones ( r = 0.34, p < 0.001; κ = 0.20, p = 0.07). Bland-Altman plots showed a large bias (Bland-Altman index: 7.5%) for total flavonoid intake. FLAV-Q demonstrated moderate reproducibility across timepoints with mean percentage differences for total flavonoid intake ranging from 22% to 37%. Bland-Altman plots indicated moderate to small bias for reproducibility (Bland-Altman index: 2.5–3.8%). Conclusions FLAV-Q demonstrates moderate to low validity and reproducibility for total flavonoids and the subclasses. Further validation for absolute intake values is necessary to understand and address the overestimation.