Methods: This study used a mixed methods design consisting of two phases: (1) qualitative interview aimed to generate items for the first draft, and; (2) a pilot test of the second draft, followed by psychometric testing for the final draft.
Results: The first draft emerged from the qualitative interview phase including 180 items from five dimensions: (1) macronutrients-micronutrients and health; (2) nutrition and energy balance; (3) decision making on nutrition information; (4) food processing, and; (5) food safety. This first draft was evaluated for content validity by seven experts, resulting in 110 items remained. One more item was subsequently added based on the nutrition literacy literature. Therefore, the second draft consisted of 111 items. Face validity, using cognitive interview, was used to assess cognitive process, interpretation, and comprehension among 10 Thai adolescents. The second draft was then modified for appropriateness of language, and tested for reliability in 275 Thai adolescents, obtaining a reliability (KR-20) of 0.85. The item analysis for the third draft revealed that 61 items achieved the criteria.
To assess the construct validity, the third draft was tested among 442 Thai adolescents using the Thai Healthy Eating index as a gold standard. Approximately 70.59% of these Thai adolescents completed the 3-day food record. Analysis of Discrimination Index revealed that 26 items met the criteria with sufficient discrimination. However, 19 items only met baseline criteria. To assess Convergent validity, Known-Group Technique was used, and revealed that the energy balance dimension of the healthy group had a higher nutrition literacy score than the unhealthy group. The KR-20 of the 61 items was 0.83.
Conclusion: The nutrition literacy assessment tool for Thai adolescents had sufficient reliability and validity, and may be usefully applied in nutrition literacy screening of various Thai adolescents.