Assessment of Construct Validity of the Oswestry Disability Index and the Scoliosis Research Society-30 Questionnaire (SRS-30) in Patients With Degenerative Spinal Disease.

STUDY DESIGN

Observational cohort study.

OBJECTIVES

To measure and compare the structural validity of the Oswestry Disability Index (ODI) and the Scoliosis Research Society-30 (SRS-30) questionnaire in an adult population with prolonged degenerative thoracolumbar disease.

SUMMARY OF BACKGROUND DATA

The ODI and the SRS-30 are commonly used patient-reported outcome instruments to assess back-specific disability and symptoms related to scoliosis. Still, these instruments have not been validated for degenerative spinal disease with different stages of deformity.

METHODS

Altogether, 637 consecutive adult patients with degenerative spinal pathologies were included. The patients completed the ODI (version 2.0), the 23 preoperative items of the SRS-30, a general health survey, the Kasari Frequency Intensity Time (FIT) index, the Depression Scale (DEPS), the RAND-36, and visual analog scales for leg and back pain instruments. Psychometric statistical and illustrative analyses were conducted. Deformity groups were analyzed to assess how well the two instruments reflect deformity-related back problems.

RESULTS

Both instruments reflected good coverage and targeting. Correlation between the ODI and the SRS-30 was high (r = 0.70; p < .001). Both measures could distinguish between different general health states. The SRS-30 strongly reflected mental state and social well-being. The SRS-30 was less sensitive for pain and function. Furthermore, the principal component of pain/function explained more variance in the SRS-30 compared with the ODI score. The ODI was more sensitive for variance of disability among different age and deformity groups.

CONCLUSIONS

Both the ODI and the the SRS-30 provide valid scores in evaluating health-related quality of life and/or level of disability among patients with prolonged degenerative thoracolumbar disease. The ODI has slightly higher correlation with physical functioning. The SRS-30 seems to be better when evaluating the emotional and psychological functions.

LEVEL OF EVIDENCE

Level III.