How did EATS validate the DHQ and short screeners?
At the beginning of the study, participants filled out a brief questionnaire that asked
about body weight, smoking history, and physical activity. Then, during the course of a
year, the participants completed four telephone-administered 24-hour dietary recalls, with
one recall per season. Following these 24-hour recalls, participants were randomized into
two groups, each of which filled out two mail-administered FFQs, one month apart. One
group completed the DHQ and the 1995 NCI-Block Health Habits and History Questionnaire;
the other group completed the DHQ and the Willett FFQ (purple version). These versions of
these FFQs were among the most widely used FFQs in epidemiologic research at the time.
Two subgroups of participants also filled out one of the two short screeners.
Study investigators compared the performance of the DHQ to that of the Block and
Willett FFQs. To further compare the performance of the three FFQs, study investigators
determined correlations between each of the FFQs and "true" intakes, which were estimated
using a measurement error model based on the four 24-hour recalls. The short screeners
were evaluated by comparing their performance against the DHQ and the 24-hour recalls.
Analyses of the results showed that the DHQ performed as well as or better than the
other two FFQs (see Comparative Validation of the
Block, Willett, and NCI Food Frequency Questionnaires). Both short screeners were
useful in estimating median intakes of fruits and vegetables (see Performance of Two New Cognitively Enhanced
Fruit and Vegetable Short Assessment Forms).