Comparative Validation of the Block, Willett, and NCI Food Frequency Questionnaires
Summary: The 1997-1998
Eating at America's Table Study (EATS) validated a new NCI-developed food
frequency questionnaire (FFQ), the Diet History Questionnaire (DHQ), and
compared its performance to that of two other FFQs widely used at the time, the 1995 Block FFQ and
the purple version of the Willett FFQ. The DHQ
performed as well as or better than the other two FFQs. Results from this study
also point the way to future research in exploring the structure of measurement
error in current methods of assessing dietary intake.
Reference: Subar AF,
Thompson FE, Kipnis V, Midthune D, Hurwitz P, McNutt S, McIntosh A, Rosenfeld S.
Comparative Validation of the Block, Willett, and National Cancer Institute Food
Frequency Questionnaires. Am J Epidemiol 2001;154(12):1089-99.
The most practical and economical
way to collect comprehensive dietary data in large epidemiologic studies is the
food frequency questionnaire (FFQ). FFQs are designed to capture individuals'
usual dietary intake by asking respondents to report their frequency of
consumption of a list of foods over a specific period of time. Efforts to
improve the accuracy of FFQs are essential to improving our ability to measure
dietary intake patterns and thereby to better understand of the role of diet in
the etiology and prevention of chronic diseases such as cancer.
The Eating at America's Table Study
(EATS) was designed to validate the Diet History Questionnaire (DHQ), a new and
improved FFQ developed by the National Cancer Institute, and to compare it
against two other widely used FFQs -- the 1995 NCI-Block Health Habits and History
Questionnaire and the Willett (purple version) FFQ. Of the 1,640
eligible individuals recruited for the study, 1,301 participants first completed
four 24-hour dietary recalls over the course of a year. Following this phase,
participants were randomized into two groups, one of which completed the DHQ and
the Block FFQ. The other group completed the DHQ and the Willett FFQ. The DHQ
was validated by assessing the correlations and attenuation coefficients between
nutrient intakes estimated on the DHQ and "true" intakes estimated from the four
24-hour recalls using a measurement error model. The investigators also
determined correlations between the Block and Willet FFQs and these "true" intakes.
Results showed that absolute
nutrient intakes for women estimated by the DHQ and Block FFQs were fairly
comparable to the 24-hour recalls; the Willett instrument tended to overestimate
nutrient intake for women. All three instruments underestimated absolute
nutrient intake for men, compared with the recalls, though the Willett
instrument underestimated to a greater degree than did the other two FFQs.
Correlation and attenuation coefficients were somewhat higher for the DHQ than
for the Block FFQ, and both were better than the Willett FFQ in models
unadjusted for energy. Energy adjustment increased correlation and attenuation
coefficients dramatically for the Willett FFQ and modestly for the other two
FFQs, suggesting that energy adjustment, in general, reduces measurement error
in all FFQs. The lack of portion size information in the Willett FFQ may
partially explain the differences in absolute intakes among the three
FFQs.
To better understand the structure
of measurement error in FFQs, the authors urge further research in varied
populations with biomarker reference instruments that are not based on
self-report. At the same time, EATS has shown that this improved,
cognitively-based FFQ is as good as or better than two FFQs
that were in wide use at the time
and is a reasonable alternative for investigators to use in a data collection
domain that is still primarily dependent on self-reported
information.
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