Six-minute walk test is reliable and sensitive in detecting response to therapy in CIDP

The current clinical measures (ONLS, R-ODS, mRS, and MRC) may not be so sensitive in capturing minimal variations or measuring fatigue in chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). Our aim was to assess if 6-min walk test (6MWT) is able to increase the sensitivity in detecting response to therapy and to capture fatigue in CIDP patients.

We tested 6MWT in 42 CIDP patients. Using both anchor-based and distribution-based approaches, we estimated the meaningful clinical change after therapy by calculating the minimum improvement cutoff (Minimal Clinically Important Difference Score-MCID) required for considering a patient as responder. We calculated the sensitivity of the 6MWT versus the other clinical outcomes. We analysed fatigue by comparing the velocities between first and sixth minutes of the 6MWT and the effect of treatment on fatigue using an ANOVA model for repeated measures.

MCID resulted equal to 20 m. The combination of 6MWT-MCID cutoff with the other clinical measures led to identify 74% of responders. The sensitivity of the 6MWT was 90% versus 77% of the other clinical measures. The 6MWT was also sensitive in capturing fatigue-related changes, even though fatigue was not influenced by treatment.

The combination of the 6MWT with the other clinical measures increased the chance to detect the quote of responders. We propose to include the 6MWT in the routine assessment of CIDP patients and the MCID cutoff at 20 m could be set for identifying the responders and properly guiding the therapy management.