Exploratory and confirmatory factor analysis of the Arabic neck disability index: A cross-sectional study

Abstract

Objectives: Neck pain is the fourth leading cause of disability. The most common validated tool assessing its effect on the participant’s functional status is the neck disability index (NDI). We aimed to investigate the factorial structure of the Arabic NDI (NDI-Ar) using exploratory and confirmatory factor analysis (CFA) in a multioccupational sample. Methods: A cross-sectional study conducted in Saudi Arabia. A total of 641 participants completed the NDI-Ar. The Cronbach’s alpha test was used to test the reliability of the questionnaire. Exploratory factor analysis (EFA) was used to assess the existing factor structure within the 10-indicator NDI questionnaire. Parallel analysis (PA) and scree plot with the unidimensional congruence test, mean of item residual absolute loadings test, and explained common variance test were used to assess the number of the extractable factors and their unidimensionality. CFA was also carried out. Results: EFA of the NDI-Ar suggested the presence of two-factor solutions. However, the analysis with the tests of closeness to unidimensionality, PA tests, and the more rigorous CFA indicated that the two-factor solutions were not tenable, and a single latent factor solution is a better fit with the observed data measured on Middle Eastern people. Conclusion: The present study explored the factorial structure of the NDI-Ar. The two-factor solutions were not tenable and a single latent factor solution might be a better fit.