Comparison of approaches to correct intake-health associations for FFQ measurement error using a duplicate recovery biomarker and a duplicate 24h dietary recall as a reference method

Objective: To illustrate the impact of intake-related bias in FFQ and 24-hr recall and correlated errors between these methods, on intake–health associations. Design: Dietary intake was assessed by a 180-item semi-quantitative FFQ and two 24-hr recalls. Urinary N and urinary K were estimated from two 24 -hr urine samples. We compared four scenarios to correct associations for errors in an FFQ estimating protein and K intakes. Setting: Wageningen, the Netherlands. Subjects: Fifty-nine men and fifty-eight women aged 45–65 years. Results: For this FFQ, measurement error weakened a true relative risk of 2.0 to 1.4 for protein and 1.5 for K. As compared with calibration to duplicate recovery biomarkers (i.e. the preferred scenario 1), estimating a validity coefficient using this duplicate biomarker resulted in overcorrected associations, caused by intake-related bias in the FFQ (scenario 2). The correction factor based on a triad using biomarkers and 24-hr recall was hampered by this intake-related bias and by correlated errors between FFQ and 24-hr recall, and in this population resulted in a nearly perfect correction for protein but an overcorrection for K (scenario 3). When the 24-hr recall was used for calibration, only a small correction was done, due to correlated errors between the methods and intake-related bias in the 24-hr recall (scenario 4).Conclusions: Calibration to a gold standard reference method is the preferred approach to correct intake–health associations for FFQ measurement error. If it is not possible to do so, using the 24-hr recall as reference method only partly removes the errors, but may result in improved intake–health associations.

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