Validity and reliability of an FFQ for use with adolescents in Ho Chi Minh City, Vietnam.

Objective: The present study evaluates the reliability and validity of an FFQ designed for use with adolescents in urban Vietnam.
Design: A cohort study was conducted between December 2003 and June 2004. The FFQ was administered three times over a 6-month period (FFQ 1-3) and nutrient intakes were compared to those obtained from four 24 h recalls collected over the same period (24 h recalls 1-4) using crude, energy-adjusted and de-attenuated correlation coefficients. The level of agreement between the two measurements was also evaluated with Bland-Altman analysis. The percentage of nutrient intakes classified within one quintile, as well as quadratic-weighted kappa statistics, were calculated.
Setting: Ho Chi Minh City, Vietnam.
Subjects: A total of 180 students were recruited in three junior high schools.
Results: Coefficients ranged from 0.22 for retinol to 0.78 for fibre for short-term reliability, and from 0.30 for retinol to 0.81 for zinc for long-term reliability. Coefficients for nutrient intakes between the mean of the three FFQ and mean of four 24 h recalls were mostly around 0.40, but higher for energy-adjusted nutrients. After allowing for within-person variation, the mean coefficient was 0.52 for macronutrients and 0.46 for micronutrients. There were a relatively high proportion of nutrient intakes classified within one quintile and a small number grossly misclassified. Kappa values shows 'fair' to 'good' agreement for all food/nutrient categories, while the Bland-Altman plots indicated that the FFQ is accurate in assessing nutrient intake at a group level.
Conclusions: This newly developed FFQ is a valid tool for measuring nutrient intake in adolescents in urban Vietnam.