Background and aims Most of clinical scales used in the assessment of acute bronchiolitis are not validated or are partial validated. The objective of this study is the validation of a clinical scale in the assessment of acute bronchiolitis (AB).

Material and methods Validation of a clinical severity scale in the context of a randomised, double-blind, clinical trial. 148 infants hospitalised with moderate acute bronchiolitis for 2 epidemics (2011–2013) were included. Demographics and clinical data were recorded. Different observers assessed all patients at admission and three times daily until discharge with Wood-Downes modifies by Ferres (WDF) scale. Mild bronchiolitis and those with severity risk factors were excluded. The primary outcome was the difference in the numeric rating scale since admission until were discharged from hospital or admitted to PICU. The collected variables were analysed using non-parametric tests. In all cases it was considered a significance level of 95%.

Results Mean age and range interquartílico [IQR] 1.5 months (1–3), 50% were male. The WDF scale in patients admitted to PICU was significantly higher (6 (4–8) vs 5 (4–8), p = 0.026). The WDF scale decreased an average of 3.87 points (95% CI, 2.5–6.5) from admission to the time of discharge.

Conclusions Our results suggest that the WDF scale is related to the severity and outcome of patients with acute bronchiolitis at admission and at discharge. It´s change from admission to discharge, which show a clear decrease adequately, reflect good clinical evolution necessary for discharge home.