NPPB and pulmonary arterial hypertension: In a small cohort of SSc-PAH patients (n = 15), ADMA levels were significantly associated with PAH, and the combination of ADMA levels ≥ 0.7 ng/mL and N-terminal pro B-type natriuretic peptide (NT-proBNP) ≥ 210 ng/mL showed 100% sensitivity and 90% specificity for the presence of SSc-PAH, respectively [41]; another study found a negative correlation between serum ADMA levels and the 6-minute walking distance (6MWD) in patients with SSc-PAH [42].