Plasma levels of N-terminal proatrial natriuretic peptide in children are dependent on renal function and age.

Plasma levels of natriuretic peptides are used as diagnostic markers of heart failure. The aim of this study was to analyse the relation between plasma levels of N-terminal proatrial natriuretic peptide (Nt-proANP) and renal function, and to develop reference values in children. Nt-proANP was measured in the plasma of 86 patients whose glomerular filtration rate (GFR) was determined by use of the X-ray contrast medium iohexol and a fluorescence technique. Blood samples for Nt-proANP were also collected in 399 reference children, aged 0 - 15 years. The relationship between Nt-proANP and GFR was examined using a multiple regression analysis. The mean value of Nt-proANP was markedly higher in children with heart failure than in children with malignant or urologic diseases (p<0.001). The variability in plasma levels of Nt-proANP was mainly (adjusted R2=0.81) explained by the following four variables: presence of heart failure, GFR, age and previous treatment with anthracyclins. Plasma levels of the peptide are raised at birth, but fall rapidly to adult levels. We conclude that the plasma levels of Nt-proANP are age-dependent. Moderately elevated values were registered in children with severe renal impairment. Heart failure is regularly associated with excessive elevation of Nt-proANP in plasma. Our findings suggest that the influence of heart failure on levels of this peptide in children greatly exceeds the influence of renal dysfunction.