Objective: To provide further validation of the treadmill test by assessing its 'test-retest' reproducibility. Patients and Methods: In this prospective study, 28 patients with severe lumbar spinal stenosis underwent exercise treadmill testing, first at a walking speed of 1.2 mph and then at the patient's preferred walking speed. All patients had a second treadmill examination or 'retest.' No treatment intervention was performed between the initial test and the retest. Time to first symptoms (TFS) and total ambulation time (TAT) were measured. Differences between the baseline examination and the retest examination were assessed by using the concordance correlation coefficient (CCC) as well as graphically. Results: There was good reproducibility between baseline test and retest results for all 4 end points: 1.2 mph, TFS (CCC = 0.90); 1.2 mph, TAT (CCC = 0.89); preferred walking speed, TFS (CCC = 0.98); and preferred walking speed, TAT (CCC = 0.96). The median difference between trials was not significantly different from zero for any of the 4 outcomes. Conclusions: Exercise treadmill testing has good test-retest reproducibility. There was no learning phenomenon associated with the test procedure. The study further validates the clinical utility of exercise treadmill testing in patients with lumbar spinal stenosis and neurogenic claudication.
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