Dimensionality, internal consistency, and item analysis of the national health and nutrition examination surveys activities of daily living instrument among patients with report of low back pain

Objective: To measure selected psychometric properties of individual item responses from the National Health and Nutrition Examination Surveys (NHANES) activities of daily living (ADL) instrument among a population of patients with low back pain (LBP). Methods: The study group consisted of 926 individual attendees of a traditional medical appointment. All subjects had self-reported LBP and completed questions within the NHANES ADL instrument, a 16-item questionnaire designed to represent the internal latent construct of ADL. Data analyses included exploratory factor analysis, internal consistency measures, and polytomous (graded) item response theory. Results: The NHANES ADL instrument is a unidimensional and internally consistent measure of ADL. Graded item response theory analyses indicated that although some variability exists, all 16 single items were sensitive measures of the latent construct of ADL. Most item responses demonstrated high discrimination. Conclusion: Individual use of selected items of the NHANES ADL instrument may further improve the capacity of the health care provider in measuring and recording dysfunction associated with LBP.