How to use N-terminal pro-brain natriuretic peptide (NT-proBNP) in assessing disease severity in bronchiolitis

Bronchiolitis is a common viral illness which can lead to severe respiratory compromise and can coexist with or mask cardiac failure. Brain natriuretic peptide (BNP) and the inactive portion of its pro-hormone: N-terminal pro-BNP (NT-proBNP) are excreted in response to cardiomyocyte stretching and are established biomarkers in cardiac failure. Here, we discuss the technicalities of NT-proBNP testing and review available evidence regarding NT-proBNP testing in bronchiolitis. We identified and appraised seven studies assessing the role of BNP or NT-proBNP as biomarkers of bronchiolitis severity, in children with and without underlying congenital cardiac disease. One study of 76 children with dyspnoea showed that the median NT-proBNP level in children with cardiac failure was 7321 pg/mL vs 241 pg/mL in children with a respiratory cause of dyspnoea vs 87.21 pg/mL in healthy controls (p<0.05). A cut-off of 726 pg/mL could aid differentiation between cardiac and respiratory causes of respiratory distress. Other evidence showed a positive correlation between BNP levels and bronchiolitis severity, and that raised BNP can predict acute heart failure in children with congenital cardiac disease presenting with bronchiolitis. However, most studies consisted of small cohorts with conflicting evidence between them. Furthermore, several studies assessed BNP rather than NT-proBNP directly. BNP has a shorter half-life, which may affect analysis. In conclusion, NT-proBNP is a rapid and inexpensive test with the potential to be a useful biomarker in severe bronchiolitis and cases complicated by acute cardiac failure. However, studies with larger cohorts are required to better establish this role.