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Measurement error correction for nutritional exposures with correlated measurement error: Use of the method of triads in a longitudinal setting
Author(s) -
Rosner Bernard,
Michels Karin B.,
Chen YaHua,
Day Nicholas E.
Publication year - 2008
Publication title -
statistics in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.996
H-Index - 183
eISSN - 1097-0258
pISSN - 0277-6715
DOI - 10.1002/sim.3238
Subject(s) - statistics , european prospective investigation into cancer and nutrition , standard error , lambda , mathematics , observational error , random error , nutritional epidemiology , systematic error , measure (data warehouse) , limits of agreement , bland–altman plot , medicine , computer science , confidence interval , physics , nuclear medicine , data mining , epidemiology , optics
Nutritional exposures are often measured with considerable error in commonly used surrogate instruments such as the food frequency questionnaire (FFQ) (denoted by Q i for the i th subject). The error can be both systematic and random. The diet record (DR) denoted by R i for the i th subject is considered an alloyed gold standard. However, some authors have reported both systematic and random errors with this instrument as well. One goal in measurement error research is to estimate the regression coefficient of T i (true intake for the i th subject) on Q i denoted by λ TQ . If the systematic errors in Q i and R i (denoted by q i and r i ) are uncorrelated, then one can obtain an unbiased estimate of λ TQ by λ RQ obtained by regressing R i on Q i . However, if Corr( q i , r i )>0, then λ RQ >λ TQ . In this paper, we propose a method for indirectly estimating λ TQ even in the presence of correlated systematic error based on a longitudinal design where Q i (surrogate measure of dietary intake), R i (a reference measure of dietary intake), and M i (a biomarker) are available on the same subjects at 2 time points. In addition, between‐person variation in mean levels of M i among people with the same dietary intake is also accounted for. The methodology is illustrated for dietary vitamin C intake based on longitudinal data from 323 subjects in the European Prospective Investigation of Cancer (EPIC)‐Norfolk study who provided two measures of dietary vitamin C intake from the FFQ ( Q i ) and a 7‐day DR ( R i ) and plasma vitamin C ( M i ) 4 years apart. Copyright © 2008 John Wiley & Sons, Ltd.