Six-minute walk test in systemic sclerosis: A systematic review and meta-analysis

Background: Pulmonary arterial hypertension (PAH) and interstitial lung disease (ILD) are the leading causes of death in systemic sclerosis (SSc). Although the six-minute walk test (6MWT) is generally used for evaluating PAH and ILD, utility in SSc is undetermined. This study evaluates the role of 6MWT in SSc by systematic review and meta-analysis.

Methods: A systematic literature search on PubMed, Web of Science and Cochrane Library Online was performed using the medical subject heading search terms for "systemic sclerosis", "CREST" and "six minute walk test", "six minute walk distance (6MWD)", "(cardiopulmonary) exercise test", "treadmill test" or "step test".

Results: Meta-analysis of 43 included studies (3185 SSc-all patients) revealed that the mean 6MWD was comparable between the SSc-PAH and SSc-ILD-PH subgroups (288m [95% CI: 259-317m] vs 286m [95% CI: 259-314m], p=0.93). The pooled mean of 725 SSc-PAH patients was significantly lower than the pooled mean of 413 SSc-noPAH patients (430m [95% CI: 402-458m], p<0.001). 95 SSc-ILD-PH patients walked significantly less than 328 SSc-ILD patients (388m [95% CI: 362-415m], p<0.001) and significantly less than 86 SSc-noILD patients (420m [95% CI: 325-515m], p=0.008). 81-98% of the SSc-PAH/ILD/ILD-PH patients performed a 6MWT.

Conclusions: During a 6MWT, SSc-PAH patients walk less than SSc-noPAH patients and SSc-ILD-PH patients walk less than SSc-ILD and SSc-noILD patients.