The serum levels of C-reactive protein, average platelet volume, total bilirubin, serum uric acid, homocysteine, ferritin, and N-terminal brain natriuretic peptide precursor (NT-proBNP) in CTD-with PAH patients were distinctly higher than those in CTD-without PAH patients (all P < 0.05, Table 1). Here, CRP is linked to pulmonary arterial hypertension.