RESUMEN
OBJECTIVE: To adapt a short FFQ (SFFQ) and evaluate its relative validity and reproducibility to assess food group intake in a population resident in the Basque Country. Moreover, the possible influence of associated variables (such as education level) on its validity and reproducibility was determined. DESIGN: Nine-day 24-h recalls (24HR) were used as a reference to explore validity over the course of 1 year. The degree of misclassification in the SFFQ was evaluated by a contingency table of quartiles and by Bland-Altman plots comparing SFFQ2 and 24HR. SFFQ was administered twice to explore reproducibility at 1 year. SETTING: Basque Autonomous Community. PARTICIPANTS: Adults aged ≥21 years (n 99). The sample was randomly selected and representative of the target population. RESULTS: For validity, statistically significant correlations were observed for more than half of the food groups, with the lowest correlations (r or ρ) for fat (-0·008) and the highest for other foods (0·963). The mean percentage of the subjects' food intake that was classified into the same or adjacent quartile in both methods was 75·2 %. Reproducibility was explored by the correlation coefficient and ranged from 0·201 to 0·809, and 82·6 % of participants were in the same or adjacent quartile in both SFFQ. The associated variables did not seem to influence the validity and reproducibility of the SFFQ. CONCLUSIONS: An adapted SFFQ presented good reproducibility and validity for measuring most food groups in the target population, and these results did not seem to be influenced by the associated variables.