A prospective, longitudinal study evaluating the baseline six-minute walk test as an individual reference value in systemic sclerosis patients.

Objectives: Interstitial lung disease (ILD) and pulmonary arterial hypertension (PAH) are the leading causes of death in systemic sclerosis (SSc). Although the six-minute walk test (6MWT) is used for evaluating ILD and PAH, no data are available on the evolution of the six-minute walk distance (6MWD) in SSc patients without ILD and PAH and whether the baseline 6MWD could serve as individual reference value for the management of those who will develop PAH or ILD.
Methods: Prospectively collected data of the first 6MWT (at baseline or 6-month follow-up) and the 6MWTs at 18-, 30-, 42-, 54-, and 66-month visit of 165 consecutive SSc patients without ILD and PAH, included in the Ghent University SSc Cohort between May 2006 and December 2016 were analysed.
Results: 96-100% of the included patients performed a 6MWT during the follow-up visits. The mean 6MWD during the baseline 6MWT of 165 SSc patients without ILD and PAH (35% limited, 56% limited cutaneous, 9% diffuse cutaneous SSc) was 484.20+/-92.65m with no significant difference in the 6MWD at different follow-up visits as compared to baseline. In 46 SSc patients without ILD and PAH who performed a 6MWT at baseline and at 66-month visit, the 6MWD walked at 66-month visit correlated with the baseline 6MWD (r=0.564, p<0.001).
Conclusions: In SSc without ILD and PAH, the 6MWT is feasible and the 6MWD is clinically stable over a 66 months period. Hence, the individual 6MWD might be used as individual reference value in management of those who will develop PAH or ILD.