Background: Asthma is the most common chronic respiratory disease in children. The neutrophil-to-lymphocyte ratio (NLR) is a marker of a chronic inflammatory state, however, data on the predictive role of NLR in acute asthma exacerbations in children is lacking.

Aim: To investigate the potential role of NLR in predicting the severity of acute asthma exacerbations in children.

Methods: A retrospective study, that included children aged 2-18 years, who were referred to the emergency department (ED) due to asthma exacerbation, between 2016 and 2021, and underwent a complete blood count upon arrival. NLR was assessed as a continued variable and divided into four quartiles. Association was examined between severity parameters and NLR quartiles.

Results: Eight hundred thirty-one ED visits for asthma exacerbation were included in the study. The median NLR was 1.6, 3.8, 6.7, and 12.9 in quartiles 1,2,3, and 4, respectively (p<0.001). Demographic parameters, background diseases, and chronic medications were similar between the quartiles. Higher heart rate, body temperature, systolic blood pressure, and respiratory rate were observed in the higher NLR quartiles, as well as lower oxygen saturation. Higher urgency scale and medical treatment, including intravenous Magnesium sulfate, were observed in the higher NLR quartiles, with higher admission rates and prolonged hospitalizations.

Conclusion: NLR upon admission reflects the severity of asthma exacerbation and the chances of hospitalization among children in the ED. Further studies are warranted for its implementation in the clinical setting, providing validated cutoff values in which a high probability of severe asthma is likely.