NPPB and pulmonary arterial hypertension: Although CysC proved to be a sensitive biomarker for assessing PAH, offering advantages over standard biomarkers such as BNP and NT-proBNP by being independent of muscle mass, age, and gender [20] and predicting long-term mortality and clinical events in patients with CHD–PAH [21], its utility was demonstrated only in small studies [21]; therefore, to date, CysC has no clinical use.