The North American spine society lumbar spine outcome assessment instrument - Reliability and validity tests

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.