Background and aims: We aimed to analyze the correlation of urinary with serum NT-proBNP concentrations in acute bronchiolitis and its association with the severity of the disease.  Material and Methods: A pilot observational study conducted between 1st October and 31st March 2022, including acute bronchiolitis cases who attended our institution. Serum and urinary NT-proBNP concentrations were determined using the Alere NT-proBNP assay in time-matched urine and blood samples. We explored the linear relationship between both concentrations and compared clinical outcomes indicative of severe acute bronchiolitis between groups of raised and normal urinary NT-proBNP.  Results: 17 infants (median age 68 (36-91) days) with 36 time-matched samples were included. The urinary and serum concentrations of NT-proBNP were significantly correlated with (r=0.867 & R-squared coefficient=0.751; p<0.001). The log-10-transformed urinary NT-proBNP concentrations were higher at the time of hospital admission in those infants that required PICU admission with ventilatory support compared with those without this outcome (1.85 (1.16-2.44) pg/mg vs 0.63 (0.45-0.84) pg/mg); p<0.001); and resulted positively and strongly correlated with the duration of the ventilatory support (rho=0.76; p<0.001) and the LOS hospitalization (rho=0.84; p<0.001) Conclusion: The measurement of urinary NT-proBNP concentrations could be a reliable surrogate for serum NT-proBNP levels highlighting the potential value of the urinary NT-proBNP as a non-invasive tool to assess severity in acute bronchiolitis.

Objective: To evaluate if hypoalbuminemia on admission predict disease severity in children with acute bronchiolitis (AB). Working hypothesis: Hypoalbuminemia is associated with worse outcome in infants with AB. Study design: Single-centre prospective cohort study. Patient-subject selection: Infants aged <12 month-old with AB. Methodology: Serum albumin levels were determined within the first 24 hours upon inclusion. The primary outcome was the need of pediatric intensive care unit (PICU) admission. Results: We enrolled 90 cases of AB. Serum albumin was independently associated with C-Reactive protein levels (CRP) (rs=-0,28; p=0.002). Fourteen (15.5%) cases required PICU admission. They presented lower serum albumin levels (3.7 (0.11) vs 4 (0.5) g/dl; p=0.034) regarding those patients without severe illness. In the multivariate logistic regression analysis, hypoalbuminemia was independently associated with a higher risk of severe illness (adjusted Odds Ratio 4.1 (1.2-85); p=0.032). The area under the ROC curve for serum albumin to predict adverse outcome was 0.70 (95% Confidence interval of 0.59-0.79). A cut-off point of 3.5 g/dl presented a sensitivity of 0.71, specificity of 0.68, positive predictive value of 0.29, and negative predictive value of 0.92. Conclusion: Low serum albumin levels at admission are significantly associated with higher PICU admission rates in infants with AB. The inflammatory response could play a key role in the occurrence of hypoalbuminemia in AB.