Validity and reproducibility of a precoded questionnaire to assess fruit and vegetable intake in European 11-to 12-year-old schoolchildren

BackgroundlAims: Validity and reproducibility were evaluated of a new questionnaire to assess fruit and vegetable intakes in 11- to 12-year-old children. Methods: The precoded teach er-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). Results: 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. Conclusion: 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.