NPPB and Patent ductus arteriosus: Another study of El-Khuffash et al. has also shown that NT-proBNP on day 3 significantly correlated with LA/Ao ratio, and PDA diameter.31 A low NT-proBNP level could therefore represent an independent marker of PDA spontaneous closure at a time when classical echographic signs are poorly predictive of spontaneous evolution of the PDA.32 The peak plasma NT-proBNP level on day 2 at 7252 pmol/ml offered the best predictive values for HsPDA.