Lack of specificity of the 6-minute walk test as an outcome measure for patients with systemic sclerosis.

OBJECTIVE

The 6-minute walk test (6MWT) is an important prognostic tool in various cardiovascular diseases and has been considered as a surrogate endpoint. However, conflicting results have been reported in systemic sclerosis (SSc). Our objective was to evaluate the relationships of the 6-min walking distance (6MWD) and organ damage in SSc.

METHODS

Eighty-seven consecutive patients with SSc were included and prospectively investigated; they underwent 6MWT in addition to conventional assessment of possible lung, heart, kidney, skin, and muscle involvement, and disease activity scoring, severity, and quality of life determination.

RESULTS

Twenty-six patients (30%) had an abnormal 6MWT and the mean 6MWD was 461.8 +/- 103.0 m. When considering 6MWT as a binary variable - normal or abnormal - C-reactive protein (CRP) was the only independent variable associated with abnormal 6MWT. Considered as a continuous variable, the 6MWD was associated with measures of lung involvement and inflammation, with the activity and severity of disease, and also with quality of life; nevertheless, calcinosis was the only independent factor associated in multivariate analyses with a trend for an association for CRP.

CONCLUSION

The 6MWD relates to broad factors in SSc and these results raise doubts about the specificity of the 6MWD in this systemic disease, and its relevance to monitoring therapy.