Presented at the Neonatal Society 2008 Spring Meeting.
Ramakrishnan S1, Heung YM2, Round J3, Williams AF3 (introduced by Dr S Calvert and Dr N Kennea)
1 Neonatal Unit, St George’s Hospital, University of London, London SW17 0QT, UK
2 Department of Chemical Pathology, St George’s Hospital, University of London, London SW17 0QT, UK
3 Department of Child Health, St George’s, University of London, London SW17 0QT, UK
Aim: N-terminal pro brain natriuretic peptide (NT-ProBNP) concentrations are raised in adults and children with cardiac failure though data are few in preterm neonates1. NT-ProBNP is more stable than BNP2 and less susceptible to degeneration during specimen handling or storage. We have evaluated in a blinded prospective study the diagnostic utility of NT-ProBNP concentrations for prediction of haemodynamically significant patent ductus arteriosus (PDA) at the end of the first week of life.
Methods: Plasma NT-ProBNP was measured on days 1, 2, 3 and 7 in 100 preterm babies born before 34 weeks gestation (mean gestation 28.8 +/- 2.9 weeks; mean birth weight 1224 +/- 512g). The presence of ductal patency on day 7 was determined echocardiographically. NT-ProBNP was also measured before and after pharmacological or surgical intervention in babies who required treatment. Both the echocardiographers and treating clinicians were blinded to NT-ProBNP measurements. The Wandsworth local research ethics committee approved this study and written parental consent was obtained.
Results: Plasma NT-ProBNP concentrations generally fell by day 7. Twenty preterm babies required treatment on 27 occasions for a haemodynamically significant duct. These babies had significantly higher levels of NT-ProBNP than those without a duct on days 2, 3 and 7. The areas under receiver operating characteristic (ROC) curves were 0.896, 0.897 and 0.931 respectively (95% CI 0.815 to 1.00, p < 0.0001). NT-ProBNP concentration fell from 1726 (682-16,608) to 479 (121-3,325) pmol/l (median, range, p < 0.0018, Wilcoxon paired rank test) in successfully treated babies but did not change significantly if the duct remained open.
Conclusion: NT-ProBNP concentrations gradually declined by day 7 irrespective of duct status but were consistently higher throughout the first week in those whose duct required treatment. Plasma NT-ProBNP concentration as early as day 3 of life, predicts those preterm infants who will have a haemodynamically significant PDA at the end of the first week. A concentration greater than 2850 pmol/l at that stage has 90% sensitivity, 89% specificity (95% CI 68.30 to 98.77, likelihood ratio 8.10). A fall in plasma NT-ProBNP concentration associated with treatment is a useful indicator of closure.
References
1. el Khuffash A, Molloy EJ. Arch Dis Child Fetal Neonatal Ed 2007; 92: F320-4.
2. Puddy VF, Amirmansour C, Singer DR, Williams AF. Clin Sci (Lond) 2002; 103: 75-7.