NPPB and pulmonary arterial hypertension: In addition to its predictive ability, effective subdivision of the intermediate-risk group and accurate estimation of 1-year mortality, the ESC/ERS four-strata model is practical for clinical use, relying on three easily accessible parameters (WHO-FC, 6MWD and BNP/NT-proBNP), which have previously shown the greatest prognostic value in PAH [24, 26–29].