The association between neutrophil-to-lymphocyte ratio and anaphylaxis refractory to epinephrine treatment

Objectives: Anaphylaxis refractory to epinephrine treatment is a potentially fatal condition requiring additional medications. Neutrophil-to-lymphocyte ratio (NLR) is commonly used to predict severity in allergic diseases. The aim of this study was to determine the association between NLR and refractory anaphylaxis. Methods: This was a retrospective, observational study of 126 adult anaphylaxis patients arriving at the emergency department between January 2015 and December 2019. Patients were placed into refractory anaphylaxis, if they required more than two 0.3 mg injections of intramuscular epinephrine for symptom resolution, and non-refractory anaphylaxis groups. NLRs were determined at the time of arrival at the hospital and were compared between groups. Results: Thirty-two (25.4%) patients were categorized as refractory anaphylaxis cases. NLR was significantly lower in the refractory anaphylaxis than in the non-refractory anaphylaxis group (P < 0.001). In the multivariate logistic regression analysis model, NLR was inversely associated with the occurrence of refractory anaphylaxis (adjusted odds ratio 0.33, 95% confidence interval 0.13-0.81, P = 0.016). The area under the receiver operating characteristic curve of NLR for prediction of refractory anaphylaxis was 0.717 (P < 0.001). The optimal cut-off value of NLR was < 0.68 using the Youden index, with 50.0% sensitivity and 80.9% specificity. Conclusions: NLR was independently and inversely associated with the occurrence of refractory anaphylaxis among anaphylactic patients. Therefore, NLR has the potential to be used as an easy and inexpensive test to predict refractory anaphylaxis in patients.