a1 Channing Laboratory, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, USA
a2 Department of Nutrition, Harvard School of Public Health, USA
a3 Department of Maternal and Child Health, Harvard School of Public Health, USA
a4 Department of Epidemiology, Harvard School of Public Health, USA
a5 Department of Health and Social Behavior, Harvard School of Public Health, USA
a6 Abt Associates, USA
Objective To assess the reproducibility and validity of a semiquantitative food frequency questionnaire (FFQ) to classify children and adolescents in terms of daily servings of fruits and vegetables and intake of calories, protein, fat, carbohydrate, dietary fibre, vitamin C, phosphorous, calcium and iron.
Design FFQs were collected in the autumn of 1993 and 1994. Four 24-hour diet recalls were collected during the same 1-year period and their mean was compared to the FFQ diet estimates.
Setting Low income, inner-city state schools.
Subjects A sample of 109 inner-city fourth to seventh grade students.
Results The 1-year reproducibility of the FFQ, assessed with Spearman correlations, was lower among the fourth and fifth (range: r = −0.26 to 0.40) than the sixth and seventh grade students (range: r = 0.18–0.47). After adjusting for day-to-day variation in dietary intake, for most nutrients and foods the correlations between the FFQ and the 24-hour recalls remained greater among the junior high school students (fourth to fifth grade range: r = 0.0–0.42; sixth to seventh grade range: = 0.07–0.76).
Conclusions Inner-city sixth and seventh grade students demonstrated the ability to provide valid estimates of intake of calories, carbohydrate, calcium, phosphorous, iron and vitamin C over the past year. However, children in the fourth and fifth grades experienced some difficulty in completing the FFQ. Our results suggest that, before using this instrument with fourth and fifth grade children, investigators should assess whether study participants can think abstractly and are familiar with the concept of ‘average intake’.
(Received January 09 1998)
(Accepted January 12 1999)