Point-of-care testing for B-type natriuretic peptide in premature neonates with patent ductus arteriosus

Patent ductus arteriosus (PDA) is highly prevalent in pre-term neonates (PTN) and has been recognized as a neonatal co-morbidity. The purpose of this study was to determine if levels of brain (or B-type) natriuretic peptide (BNP), a peptide secreted by ventricular myocytes in response to volume or pressure overload, correlate with the size of the PDA. In a prospective design, 52 PTN (no PDA: n=24; PDA: n=28) were studied after obtaining parental consent. Those with genetic anomalies and congenital heart disease, except for PDA and patent foramen ovale, were excluded. Echocardiographic estimates of the diameters of the PDA (or absence of PDA) were made concurrently with capillary blood collection for BNP assay. BNP levels in samples from PTN without PDA were 23.6 ng/L (median); 13.1 to 32.3 ng/L (IQR); initial samples (between days 3 and 7 of life) with small PDA (n=11), median 66.1 ng/L; 55.5 to 85.3 ng/L (IQR); with moderate PDA (n=6) median 284 ng/L; 204 to 622 ng/L (IQR); and with large PDA (n=11) 2410 ng/L median; 420 to 2770 ng/L (IQR). (p< 0.0001 for ANOVA; groupwise: p<0.05 for both no PDA vs. moderate and large PDA); Trend analysis suggested a strong association of BNP with size of PDA (p<0.001). Of 17 subjects with moderate to large PDA, pre and post-treatment (Ibuprofen; per standard protocol) data were obtained on 12 subjects. Pre-treatment BNP ranged from 111 to 5000 ng/L; post-treatment BNP decreased to 5.0 to 262 ng/L (p = 0.0005). Estimates of decision levels for treatment were made by examining dichotomized groups, i.e., no-to-small vs. moderate-to-large and using receiver-operator characteristic (ROC) curve analysis yielding a value of 123 ng/L. BNP may obviate repeated echocardiography as follow up after treatment, or to monitor future course of respiratory distress secondary to PDA in PTN.