The validity of the SRS-22 instrument in an adult spinal deformity population compared with the Oswestry and SF-12: a study of response distribution, concurrent validity, internal consistency, and reliability.

STUDY
DESIGN: Prospective analysis of a consecutive cohort of adult spinal deformity patients queried over a 12-month period.
OBJECTIVES: To assess the SRS-22 instrument compared with the SF-12 and Oswestry. SUMMARY OF BACKGROUND DATA: Very few reports in the literature have applied the SRS-22 to adult spinal deformity patients.
METHODS: Consecutive adult spinal deformity patients were applied the SRS-22, SF-12, and Oswestry. Four analyses were done: 1) floor/ceiling effect; 2) Pearson's correlation coefficients between the SRS-22, SF-12, and Oswestry; 3) Cronbach's alpha analysis for internal consistency within the SRS-22; and 4) test/retest.
RESULTS: Floor/ceiling range for the SRS-22 compared favorably with the SF-12 and Oswestry. The Pearson's coefficients correlating the two questionnaires relative to the SRS-22 were > 0.7. The Cronbach's alpha within each domain for the SRS-22 were > 0.7, except for pain (0.67). Test/retest correlation coefficients ranged from 0.84 to 0.95 for the subscales.
CONCLUSIONS: The SRS-22 is a disease-specific instrument with the capacity to demonstrate change in health status more effectively than the SF-12 and in more domains than the Oswestry. The SRS-22 showed high criterion validity with the SF-12 and Oswestry based on Pearson's coefficients. High Cronbach's alpha scores suggested a high internal consistency within each domain of the SRS-22, except for pain (0.67). Test/retest reliability was excellent.