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The North American Spine Society Lumbar Spine Outcome Assessment Instrument: Reliability and Validity Tests

Daltroy, Lawren H. DrPH*†; Cats-Baril, William L. PhD; Katz, Jeffrey N. MD, MS*†; Fossel, Anne H.; Liang, Matthew H. MD, MPH*†

Outcome Assessment

Study Design A cross-sectional study of a convenience sample of lumbar spine patients, with a subsample followed for retest reliability.

Objectives To assess the instrument's reliability, validity, and acceptability to patients.

Summary of Background Data Patients with eight diagnoses, four before surgery and four after surgery, were recruited from six orthopedic practices to test the questionnaire.

Methods One hundred sixty-seven patients were approached through the physician's office, yielding 136 usable questionnaires (84%) and 24-hour retests on 64 patients.

Results The questionnaire took about 20 minutes to administer and was acceptable to patients. The lumbar spine pain and disability and neurogenic symptoms subscales discriminated among patient groups as hypothesized and showed significantly better scores for patients independently judged successful by their physicians after surgery. Test-retest reliability and internal reliability were high (range, 0.85-0.97). Sample sizes of 20-37 would be needed to detect a 20% difference between two groups (alpha, 0.05; beta, 0.20).

Conclusions The questionnaire should be considered for monitoring of individual patient's progress in treatment and for clinical trials.

From the *Harvard Medical School, Cambridge, Massachusetts, the Brigham and Women's Hospital, Boston, Massachusetts, and the School of Business Administration, University of Vermont, Burlington, Vermont.

Supported by a contract from the North American Spine Society and in part by NIH Grant AR36308. Dr. Katz is supported in part by an Arthritis Foundation Investigator Award.

Reprints, questionnaires, and scoring available from: North American Spine Society, 6300 N. River Road, Rosemont, Illinois, 60018-4262

Acknowledgment date: January 9, 1995.

First revision date: May 5, 1995.

Second revision date: August 8, 1995.

Acceptance date: September 26, 1995.

Device status category: 1.

Address correspondence to: Lawren H. Daltroy, DrPH; Robert B. Brigham Multipurpose Arthritis and Musculoskeletal Diseases Center; Brigham and Women's Hospital/PBB-B2; 75 Francis Street; Boston, MA 02115-6195

© Lippincott-Raven Publishers.