The Arabic Oswestry Disability Index as a Unidimensional Measure: Confirmatory Factor Analysis.

STUDY DESIGN

Cross-sectional study.

OBJECTIVE

To evaluate the structural validity of the Arabic version of the Oswestry disability index (ODI) in patients with low back pain (LBP).

SUMMARY OF BACKGROUND DATA

The Arabic ODI is currently used in clinical and research settings to assess disability, but questions remain regarding its structural validity.

MATERIALS AND METHODS

Adult patients with LBP were recruited from physical therapy departments of two hospitals in Saudi Arabia. Participants completed the Arabic ODI and the numeric pain rating scale. Exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) were conducted to examine the factor structure of the ODI. Maximum likelihood extraction and parallel analysis were used in the EFA, and the goodness-of-fit indices [χ 2 statistics, Tucker-Lewis index (TLI), comparative-fit index (CFI), root mean square error of approximation (RMSEA), and standardized root mean residual (SRMR)] were assessed in the CFA to confirm the factor structure.

RESULTS

A total of 113 patients (47.8% male, 52.2% female) participated. The EFA identified a unidimensional structure for the Arabic ODI, with one factor explaining 45.8% of the total variance. All items had significant factor loadings, with loadings ranging from 0.48 (sleeping) to 0.84 (sex life and social life). The CFA confirmed this unidimensional structure, yielding good fit indices [χ 2 =49.53, P <0.04; TLI=0.96; CFI=0.97; RMSEA=0.06 (90% CI=0.07-0.10), SRMR=0.04]. All ODI items exhibited significant positive loadings consistent with the expected correlation between the single latent variable (LBP-related disability) and the ODI items. A high error covariance was observed between items related to walking and standing.

CONCLUSION

The Arabic Oswestry disability index demonstrates sufficient structural validity as a unidimensional measure of disability in Arabic-speaking patients with low back pain. These findings support the continued use of the Oswestry disability index for disability assessment in clinical and research settings and support the validity of using one total score representing the single underlying latent construct.

LEVEL OF EVIDENCE

Level III.