Minimal Clinically Important Difference in the Self-Measured 6-Minute Walking Test in Patients with Sciatica Undergoing Epidural Steroid Injection.

BACKGROUND

Minimal clinically important differences (MCIDs) serve as indicators of treatment success in spine patients. While MCID values for patient-reported outcome measures are well-established within conservative treated patients with sciatica, there is scarce evidence regarding MCID values for objective outcome tests (e.g., 6-minute walking test [6WT]) that assess a patient's physical capacity.

METHODS

Forty-five patients (mean, 51 years; standard deviation, 13; 53% female) with sciatica due to degenerative lumbar disorders scheduled for epidural steroid injection (ESI) were assessed at baseline and 6 weeks after the intervention. Patients self-assessed their physical capacity using the 6WT as well as their subjective disability using several patient-reported outcomes. MCID values were calculated for raw 6-minute walking distance (6WD) (in m) and standardized 6WT z scores using three different computation methods and the following established patient-reported outcomes as anchors: visual analog scale (VAS) leg, VAS back, and Oswestry Disability Index.

RESULTS

The mean 6WD improved from 456.7 m (92.4) to 507 (89.7) and z score improved from -1.0 (1.1) to -0.7 (1.2). MCID values were ranging from 23 m (z score of 0.3) based on VAS leg to 76 m (z score of 0.7) based on the VAS back. The average MCID of the 6WT across all anchors and computation methods was 54 m (z score of 0.6). According to the average MCID of raw 6WD or 6WT z scores, 40% of patients are classified as responders to ESI for both parameters.

CONCLUSIONS

A change of 54 m in 6WD (z score change of 0.6) results in a clinically meaningful change in functional status in patients with sciatica undergoing ESI.