Validity and systematic error in measuring carotenoid consumption with dietary self-report instruments.

Auteur(s) :
Pierce JP., Natarajan L., Newman VA., Rock CL., Flatt SW., Thomson CA., Al-delaimy WK., Pi-Sunyer FX., Gamst AC., Major JM.
Date :
Avr, 2006
Source(s) :
American journal of epidemiology. #163:8 p770-8
Adresse :
Division of Biostatistics, University of California, La Jolla, CA, USA. loki@math.ucsd.edu

Sommaire de l'article

Vegetables and fruits are rich in carotenoids, a group of compounds thought to protect against cancer. Studies of diet-disease associations need valid and reliable instruments for measuring dietary intake. The authors present a measurement error model to estimate the validity (defined as correlation between self-reported intake and « true » intake), systematic error, and reliability of two self-report dietary assessment methods. Carotenoid exposure is measured by repeated 24-hour recalls, a food frequency questionnaire (FFQ), and a plasma marker. The model is applied to 1,013 participants assigned between 1995 and 2000 to the nonintervention arm of the Women’s Healthy Eating and Living Study, a randomized trial assessing the impact of a low-fat, high-vegetable/fruit/fiber diet on preventing new breast cancer events. Diagnostics including graphs are used to assess the goodness of fit. The validity of the instruments was 0.44 for the 24-hour recalls and 0.39 for the FFQ. Systematic error accounted for over 22% and 50% of measurement error variance for the 24-hour recalls and FFQ, respectively. The use of either self-report method alone in diet-disease studies could lead to substantial bias and error. Multiple methods of dietary assessment may provide more accurate estimates of true dietary intake.

Source : Pubmed
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