6-minute walk test reproducible, useful in systemic sclerosis
A recent study has demonstrated the robust reproducibility for the 6-minute walk distance (6MWD) and established the utility of the 6-minute walk test (6MWT) in examining the overall prognosis of patients with systemic sclerosis (SSc).
In total, 56 patients (aged 46±12.7 years; 38 female), with 17±10 modified Rodnan skin score (mRSS) and 1±0.8 Scleroderma Health Assessment Questionnaire (SHAQ) at first referral, were included. Overall, 277 6MWT assessments (5±3.9 6MWT per patient) were conducted over 23±22.5 months of follow-up. There were eight deaths (87.5 percent SSc-related) reported.
The 6MWD absolute value had a mean of 457±117 m, with a mean Borg dyspnoea score of 4±2.2. The 6MWD intraclass correlation coefficient was 0.996 (95 percent CI, 0.995–0.999; p<0.0001).
Multivariate linear regression analysis showed the following factors to be independently associated with a lower 6MWD: sex (R2, 0.47; p<0.0001), mRSS (R2, 0.47; p=0.008), tendon friction rub (R2, 0.47; p=0.003), SHAQ (R2, 0.47; p=0.02), muscle disability score (R2, 0.47; p=0.03), DLCO% (R2, 0.47; p=0.0008), and left ventricular ejection fraction (R2, 0.47; p=0.006).
The 6MWD at first referral independently predicted overall mortality (hazard ratio [HR], 0.99; 0.988–0.999) and SSc-related mortality (HR, 0.99; 0.988–0.999).
This observational study consecutively enrolled all patients with SSc who underwent at least two 6MWT within a minimum 3-month interval plus simultaneous routine clinical, biological and functional evaluations over 6 years. In compliance with the American Thoracic Society guidelines, each 6MWT was repeated twice to assess the reproducibility of the 6MWD, with the highest value being reported for subsequent analysis.