Correlation between urinary and serum NT-proBNP in acute bronchiolitis: A pilot study

Background and Aims: We aimed to analyze the correlation of urinary with serum N-terminal pro-brain natriuretic peptide (NT-proBNP) concentrations and its association with severity in acute bronchiolitis. Material and Methods: A pilot observational study was conducted between October 1, 2021 and March 31, 2022 including acute bronchiolitis cases who attended our institution. Serum and urinary NT-proBNP concentrations were determined using the Alere i NT-proBNP assay in time-matched urine and blood samples. The Mann-Whitney U test, Spearman's correlations, and simple linear regression were utilized to analyze the association of urine NT-proBNP levels with serum NT-proBNP and with variables indicative of severe bronchiolitis. Results: Seventeen infants (median age 68 [IQR: 36-91] days) with 36 time-matched samples were included. The urine NT-proBNP was positively and strongly correlated with the serum NT-proBNP concentrations (Spearman's rho = 0.81 & R-2 coefficient = 0.751; p < 0.001), and increased with higher C-reactive protein, (p = 0.004), procalcitonin (p = 0.001), and pCO(2) (p = 0.029) levels. The initial urinary NT-proBNP concentrations were higher in those infants that required ventilatory support compared with those without this outcome (1.85 [IQR: 1.16-2.44] vs. 0.63 [IQR: 0.45-0.84] pg/mg); p < 0.001); and resulted positively and strongly correlated with the duration of the ventilatory support (Spearman's rho = 0.76; p < 0.001) and the length of stay hospitalization (Spearman's rho = 0.84; p < 0.001). Conclusion: The urinary NT-proBNP concentrations could be a reliable surrogate for serum NT-proBNP levels and resulted elevated in cases of acute bronchiolitis with complicated evolution, suggesting a potential as a noninvasive tool to assess severity in this setting.