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

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.

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.

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.

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.