Six-minute walk distance as a marker for disability and complaints in patients with systemic sclerosis

Background. The role of the six-minute walk distance (6MWD), measured by a six-minute walk test (6MWT), in the assessment of systemic sclerosis (SSc) patients remains to be evaluated. Here, we have analysed whether 6MWD is associated with clinical parameters obtained by an extended standardised assessment of SSc patients. Methods. In 101 consecutive SSc patients, 6MWD was correlated with disease activity, Scleroderma Health Assessment Questionnaire (SHAQ) score, nutrition status, age, ESR, haemoglobin values, and several lung function parameters. Results. Of the 101 SSc patients, 6 patients were excluded because of diseases that could influence the result of the 6MWT, such as asthma, COPD or peripheral vascular disease. In the remaining 95 patients the median 6MWD was 491.0 m (range 86.0-664.5 m). 6MWD weakly-to-moderately correlated with predicted FVC, FEV1, TLC, DLCO and nutrition status. Moderate negative correlations were found for the SHAQ score and disease activity, weaker correlations for age and BMI. Exclusion of patients with musculoskeletal limitations revealed similar results. Training status of the patients did not affect 6MWD. Multivariate analyses revealed SHAQ score and predicted DLCO values as the best parameters predicting 6MWD. Optimal 6MWD cut-off values for the presence of PAH, predicted FVC values <80%, and dyspnea NYHA III / IV were between 465 m and 480 m. Conclusion. 6MWD is a surrogate marker for disability and complaints in SSc patients. Therefore, 6MWT could provide a valuable outcome parameter although it lacks organ specificity.