When comparing all three PDA grades of preterm infants with available NT-proBNP of the first week of life (no PDA: n = 17, nhsPDA: n = 36 and hsPDA: n = 8), NT-proBNP serum levels appeared to increase with hemodynamic relevance of PDA in the first week of life, but differences in NT-proBNP levels did not reach statistical significance (Fig. 2). The gene discussed is NPPB; the disease is Patent ductus arteriosus.