Echocardiography and pulmonary function as screening tests for pulmonary arterial hypertension in systemic sclerosis

Objective. A prospective study to evaluate echocardiography and gas transfer (DLCO) by comparison with cardiac catheterization in discriminating between patients with and without systemic sclerosis-associated pulmonary arterial hypertension (SScPAH). Method. A total of 137 (52 with and 85 without pulmonary fibrosis) had echocardiography and lung function tests within 3 months of their definitive invasive study. Results. At cardiac catheterization 99 of these patients were found to have PAH, while PAH was excluded in 38. Echocardiographically estimated tricuspid gradient (TG) showed a moderate positive correlation (r(2) = 0.44, P < 0.005) with both mean pulmonary pressure and invasively determined tricuspid gradient. DLCO showed a weak correlation (r(2) = 0.09, P = 0.006), when compared with mean pulmonary arterial pressure. In total, 97% of patients with an echocardiographically determined TG of > 45 mmHg were found to have pulmonary hypertension at catheterization. However, no threshold could be defined with either screening test that safely excluded PAH. Conclusions. The positive predictive accuracy of currently used non-invasive tests are adequate for the diagnosis of advanced PAH provided sufficiently high thresholds (TG > 45 mmHg or DLCO < 55% predicted) are used. These tests cannot be relied upon to exclude pulmonary hypertension where pre-test probability is high.