The Oswestry Disability Index is not a good measure for low back pain in adolescents: A Rasch analysis of data from 200 people.

OBJECTIVE

To evaluate the psychometric properties of the modified Oswestry Disability Index in adolescents with low back pain through Rasch analysis.

DESIGN

This is a psychometric study.

SETTING

Physical therapy clinics of a large pediatric hospital in Columbus, Ohio (United States).

SUBJECTS

Two hundred adolescent patients with low back pain (112 female, 15.4 ± 1.9 years old).

MAIN MEASURE

The modified Oswestry Disability Index.

RESULTS

The mean modified Oswestry Disability Index score was 17.1 ± 12.1, with scores ranging from 0 to 56 on the 100-point scale. The Rasch person reliability for the Oswestry Disability Index was 0.70, representing minimal acceptable person reliability. The Oswestry Disability Index demonstrated poor item spacing, hierarchy, and targeting of the adolescents' disability level (>1 logit between person mean and item mean). A significant misfit was observed in three of 10 items. There were significant issues with the functioning of responses on all items of the Oswestry Disability Index. Principal component analysis of residuals revealed a ratio of 5.3:1, demonstrating acceptable unidimensionality.

CONCLUSION

Due to multiple psychometric issues, the Oswestry Disability should not be used to assess disability in adolescents with low back pain. The Oswestry Disability Index significantly mistargets adolescent ability and only provides an acceptable assessment of the most disabled adolescents.