NPPB and Patent ductus arteriosus: In infants spontaneously closing at 7 days of age or earlier, the median NTproBNP on day three was 1810 ng/L (IQR, 1760–6000 ng/L) compared to infants closing spontaneously at more than seven days, 10,900 ng/L (6120–19,200 ng/L); or infants treated for PDA either with ibuprofen only, 14,600 ng/L (7740–28,100 ng/L); or undergoing PDA surgery, 32,300 ng/L (29,100–35,000 ng/L), Table 3.