Background: Pulmonary involvement is the leading cause of systemic sclerosis (SSc)-related deaths. A simple test to evaluate exercise capacity is the 6-min walk test (6MWT), and the walk distance is used as a primary outcome in clinical trials. Hemoglobin desaturation during a 6MWT is predictive of mortality in patients with primary pulmonary hypertension. Our objectives were to evaluate the walk distance and resting oxygen saturation − oxygen saturation after the 6-min period (ΔSat) during the 6MWT in patients with SSc, and to establish correlations between the 6MWT results and other clinical variables.
Methods: We analyzed 110 SSc patients. ΔSat was defined as a fall of end-of-test saturation ≥ 4%. Clinical and demographic data were collected. All the patients were submitted to chest radiographs and high-resolution CT (HRCT) and underwent pulmonary function testing and echocardiography, and the presence of autoantibodies was determined.
Results: The variables associated with a walk distance < 400 m (p < 0.05) were age, dyspnea index, fibrosis on radiography, pulmonary arterial systolic pressure (PASP) ≥ 30 mm Hg, and desaturation. The variables associated with ΔSat (p < 0.05) were age, positive anti-Scl-70 autoantibody, dyspnea index, fibrosis on radiography, FVC < 80% of predicted, PASP ≥ 30 mm Hg, and ground-glass or reticular opacities on HRCT. In the multivariate logistic regression analysis, three variables were significant when tested with walk distance: age, race, and dyspnea index; four variables were significant when tested with ΔSat: age, dyspnea index, positive anti-Scl-70 autoantibody, and FVC < 80% of predicted.
Conclusions: Desaturation during a 6MWT provides additional information regarding severity of disease in scleroderma patients with pulmonary manifestations.