MEASUREMENT PROPERTIES OF A SELF-ADMINISTERED OUTCOME MEASURE IN LUMBAR SPINAL STENOSIS

Study Design. The measurement properties and validity of a newly devel oped patient questionnaire for the assessment of patients with lumbar spinal stenosis was tested in an ongoing prospective multicenter obser vational study of patients undergoing decompressive surgery in three t eaching hospitals. Objective. The goal of the study was to develop a s hort, self-administered questionnaire on symptom severity, physical fu nctional status, and patient satisfaction. Summary of Background Data. The measure is intended to complement existing generic measures of Sp inal-related disability and health status. The questionnaire includes three scales with seven questions on symptom severity, five on physica l function, and six on satisfaction. Methods. The internal consistency of the scales was assessed with Cronbach's coefficient alpha on cross -sectional data from 193 patients before surgery. The test-retest reli ability was assessed on data from a random sample of 23 patients using Spearman's rank correlation coefficient. The responsiveness was asses sed on 130 patients with 6-month follow-up data using the standardized response mean. Results. The test-retest reliability of the scales ran ged 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 sign ificance, and strength of hypothesized relationships with external cri teria were as expected. Conclusions. This short self-administered spin al stenosis measure is reproducible, internally consistent, valid, and highly responsive. It can be used to complement generic instruments i n outcome assessment of patients with lumbar spinal stenosis.