Cystatin C and body surface area are major determinants of the ratio of N-terminal pro-brain natriuretic peptide to brain natriuretic peptide levels in children

BackgroundProduction of N-terminal pro-brain natriuretic peptide (NT) and BNP is equimolar. Although NT clearance occurs only in the kidneys, BNP clearance occurs in the kidneys and other organs. This study tested the hypothesis that NT/BNP ratio in children may be independently related to cystatin C (CysC), a glomerular filtration rate marker, when diastolic function and age/body size are taken into consideration.MethodsThe study included 430 children (5.3 ± 4.9 years) with heart disease who had undergone cardiac catheterization and simultaneous BNP, NT, and CysC measurements. Pulmonary capillary wedge pressure (PCWP) was used as a ventricular diastolic stretch marker. Variables showing skewed distribution were transformed into a common logarithm.ResultsUnivariate regression revealed that log NT/BNP was affected by PCWP (r = −0.12) and log CysC (r = 0.57). When age and the log of body surface area (BSA) were added to the stepwise regression, age was not adopted because of multicollinearity to log BSA, but PCWP (β = −0.10), log CysC (β = 0.22), and log BSA (β = −0.66) were independent factors of log NT/BNP.ConclusionsRenal dysfunction independently increased NT/BNP, whereas high BSA decreased it and is the greatest determinant of NT/BNP. The observation that high PCWP decreased NT/BNP may suggest that worsening heart failure slows BNP clearance from other organs, a compensatory pathway of heart failure. These factors need to be considered when assessing BNP and NT.