Third, even the different disease type (BDP-PH or not) was not the source of heterogeneity, further multi-centre and large sample studies could concentrate on some specific categories for paediatric PH, such as BPD-CH, CHD-PH, PPHN, etc. In addition, the severity of paediatric PH might vary, and it could affect the diagnostic capability of BNP and NT-proBNP. Here, NPPB is linked to cyclic hematopoiesis.