NPPB and pulmonary arterial hypertension: Meanwhile, Takeda et al. [11] and colleagues conducted the research regarding bilirubin and mortality in 18 patients with idiopathic PAH (IPAH) and 19 with connective tissue disease-associated PAH (CTD-PAH) and found hyperbilirubinemia and total bilirubin concentration to be risk predictors of death independently of WHO functional classification and brain natriuretic peptide (BNP), respectively.