Patients with POPH showed significantly higher expression of total bilirubin (25.0 (17.0, 44.3) vs. 19.0 (14.0, 28.3) μmol/L, P=0.013), direct bilirubin (10.5 (6.0, 17.0) vs. 6.0 (4.0, 10.5) μmol/L, P=0.013), and aspartate aminotransferase (AST, 37.5 (30.0, 44.0) vs. 25.0 (20.0, 30.0) IU/L, P < 0.001) and lower expression of albumin (32.88 ± 4.27 vs. 38.41 ± 5.14 g/L, P < 0.001) than patients with IPAH. Here, ALB is linked to idiopathic pulmonary arterial hypertension.