Validity and reproducibility of the norbagreen food frequency questionnaire.

Objective:To measure the validity and reproducibility of the NORBAGREEN food frequency questionnaire (FFQ).Subjects/methods:In Finland, 125 subjects aged 25-64 years sampled from the five main regions of the FINDIET 2002 Study and in Lithuania, 99 citizens of Kaunas aged 19-75 years participated in the study. Reference methods for the FFQ were two 3-day FFQs in Finland and four 24-h recalls in Lithuania. The FFQ was repeated after 6-8 months in both countries. The outcome of the FFQ1 was correlated with the outcome of the reference methods and with the outcome of repeated FFQ2. Cross-classification of food intakes by FFQ1 and the reference methods was examined in tertiles.Results:Validity correlations (FFQ vs the reference method, Spearman’s correlation) were for vegetables, fruit and bread 0.50 (P<0.01), 0.53 (P<0.01) and 0.54 (P<0.01) in Finland; and 0.55 (P<0.01), 0.31 (P<0.01) and 0.51 (P<0.01) in Lithuania, respectively. Correlations were smaller for potatoes and fish. The overall proportion categorized in the same or adjacent intake tertiles with the two instruments was over 83% in both countries. Reproducibility correlations varied between 0.51 and 0.75 in the Finnish study, and between 0.51 and 0.83 in the Lithuanian study.Conclusions:The NORBAGREEN FFQ can be used to rank subjects according to vegetable, fruit and bread consumption. Questions on fish and potato consumption need to be developed further.European Journal of Clinical Nutrition advance online publication, 5 September 2007; doi:10.1038/sj.ejcn.1602893.