Validity and Reproducibility of a Precoded Questionnaire to Assess Fruit and Vegetable Intake in European 11- to 12-Year-Old Schoolchildren

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Abstract
Validity and reproducibility were evaluated of a new questionnaire to assess fruit and vegetable intakes in 11- to 12-year-old children. The precoded teacher-assisted self-administered questionnaire included two sections: a 24-hour recall part and a food frequency part. Validity was tested in 4 countries (Denmark, Iceland, Norway, Portugal; n = 43-60 per country) using a 1-day weighed food record and 7-day food records as reference methods. Test-retest (7-12 days apart) reproducibility was assessed in 6 countries (Belgium, Denmark, Iceland, Norway, Portugal, Spain; n = 60-74 per country). Spearman rank correlations for fruit and vegetable intake according to the frequency part and the 7-day food record ranged between r = 0.40-0.53. Between 25-50% were classified into the same quartile and 70-88% into the same or adjacent quartile. Test-retest Spearman rank correlations for the food frequency part were r = 0.47-0.84. Three countries showed no significant difference between fruit intake as assessed with the 24-hour recall part and the 1-day weighed food record, and 2 countries showed no significant difference for vegetables. In the other countries, the 24-hour recall part resulted in substantially higher mean intake levels. Validity and reproducibility as to ranking of subjects were regarded to be satisfactory in all countries. Group mean intake, based on the original 24-hour part, was valid for fruit in 3 countries and for vegetables in 2 countries, and this part was subsequently adjusted to avoid overestimation, before the questionnaire was used in the Pro Children study.