Measurement Properties of a Self-Administered Outcome Measure in Lumbar Spinal Stenosis

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Abstract
Study Design The measurement properties and validity of a newly developed patient questionnaire for the assessment of patients with lumbar spinal stenosis was tested in an ongoing prospective multicenter observational study of patients undergoing decompressive surgery in three teaching hospitals. Objective The goal of the study was to develop a short, self-administered questionnaire on symptom severity, physical functional status, and patient satisfaction. Summary of Background Data The measure is intended to complement existing generic measures of spinal-related disability and health status. The questionnaire includes three scales with seven questions on symptom severity, five on physical function, and six on satisfaction. Methods The internal consistency of the scales was assessed with Cronbach's coefficient alpha on crosssectional data from 193 patients before surgery. The test-retest reliability was assessed on data from a random sample of 23 patients using Spearman's rank correlation coefficient. The responsiveness was assessed on 130 patients with 6-month follow-up data using the standardized response mean. Results The test-retest reliability of the scales ranged from 0.82 to 0.96, the internal consistency from 0.64 to 0.92, and the responsiveness from 0.96 to 1.07. The direction, statistical significance, and strength of hypothesized relationships with external criteria were as expected. Conclusions This short self-administered spinal stenosis measure is reproducible, internally consistent, valid, and highly responsive. It can be used to complement generic instruments in outcome assessment of patients with lumbar spinal stenosis.