Normal values of B type natriuretic peptide in infants, children, and adolescents

Objective: To determine normal values of plasma B type natriuretic peptide from infancy to adolescence using a commercially available rapid assay. Setting: Tertiary referral centre. Design: The study was cross sectional. Plasma BNP concentration was measured in 195 healthy infants, children, and adolescents from birth to 17.6 years using the triage BNP assay ( a fluorescence immunoassay). Results: During the first week of life, the mean (SD) plasma concentration of BNP in newborn infants decreased significantly from 231.6 (197.5) to 48.4 (49.1) pg/ml (p = 0.001). In all subjects older than two weeks plasma BNP concentration was less than 32.7 pg/ml. There was no significant difference in mean plasma BNP measured in boys and girls younger than 10 years (8.3 (6.9) v 8.5 (7.5) pg/ml). In contrast, plasma concentration of BNP in girls aged 10 years or older was significantly higher than in boys of the same age group (12.1 (9.6) v 5.1 (3.5) pg/ml, p < 0.001). Plasma BNP concentrations were higher in pubertal than in prepubertal girls (14.4 (9.7) v 7.1 (6.6) pg/ml, p < 0.001) and were correlated with the Tanner stage (r = 0.41, p = 0.001). Conclusions: Plasma BNP concentrations in newborn infants are relatively high, vary greatly, and decrease rapidly during the first week of life. In children older than 2 weeks, the mean plasma concentration of BNP is lower than in adults. There is a sex related difference in the second decade of life, with higher BNP concentrations in girls. BNP concentrations in girls are related to pubertal stage.