Item Analysis of Functional Measure Indicators in the National Health and Nutrition Examination Survey

Abstract Objective This study aimed to develop a function, activities, and participation measurement scale using the questions on the National Health and Nutrition Examination Survey (NHANES) by applying Item response theory (IRT) approaches. Design Cross-sectional. Participants Survey data was collected from 2,512 participants within the NHANES. Methods Twenty questions from the NHANES physical functioning section were included. We conducted exploratory and confirmatory factor analysis (EFA & CFA) to evaluate the factorial structure and model fit of the NHANES instrument. A multidimensional Rasch modeling was used to model the response data after confirming its model fit. To assess validity across subgroups, we conducted differential item functioning test with respect to sex and race using the three-dimensional partial credit model. Results Item fit indices indicated a good fit (RMSEA = 0.049, SRMR = 0.052, Tucker Lewis index = 0.975). Rasch analysis indicated that “Stoop/crouch/kneel,” “Stand for long periods,” and “Push/pull large objects” were the three most difficult items, while “Walk between rooms,” “Use fork/knife”, and “Leisure at home” were the easiest. The measure demonstrated good internal consistency overall (Cronbach’s α = 0.90). Conclusion The NHANES function, activities, and participation measure demonstrates sufficient evidence of reliability, internal consistency, and validity in non-institutionalized community-dwelling population.