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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

Bridwell, Keith H. MD; Cats-Baril, William PhD; Harrast, John; Berven, Sigurd MD; Glassman, Steven MD; Farcy, Jean-Pierre MD; Horton, William C. MD; Lenke, Lawrence G. MD; Baldus, Christine RN; Radake, Terri RN

doi: 10.1097/01.brs.0000153393.82368.6b
Health Services Research

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.

A total of 228 adult spinal deformity patients were administered the SRS-22, Oswestry, and SF-12 outcomes instruments. The floor/ceiling range for the SRS-22 was superior to that for the SF-12 and Oswestry. The correlation coefficients showed high concurrent validity between the SRS-22 and the other two instruments. The Cronbach’s alpha analysis demonstrated > 0.7 for the domains of self-image, function, and mental health and 0.67 for pain. Test/retest for the 48 patients demonstrated excellent reliability for the five scales.

From the Adult Spinal Deformity Study Group, Department of Orthopaedic Surgery, Washington University School of Medicine, St. Louis, MO.

Acknowledgment date: October 1, 2003. First revision date: January 26, 2004. Second revision date: June 18, 2004. Third revision date: August 5, 2004. Acceptance date: August 18, 2004.

The project was sponsored by the Spinal Deformity Study Group with an educational grant from Medtronic Sofamor Danek.

The manuscript submitted does not contain information about medical device(s)/drug(s).

Corporate/Industry funds were received in support of this work. Although one or more of the author(s) has/have received or will receive benefits for personal or professional use from a commercial party related directly or indirectly to the subject of this manuscript, benefits will be directed solely to a research fund, foundation, educational institution, or other nonprofit organization which the author(s) has/have been associated.

Address correspondence and reprint requests to Keith H. Bridwell, MD, Department of Orthopaedic Surgery, Washington University School of Medicine, One Barnes-Jewish Hospital Plaza, Suite 11300, West Pavilion, Campus Box 8233, St. Louis, MO 63110. E-mail: bridwellk@wustl.edu

© 2005 Lippincott Williams & Wilkins, Inc.