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.