Role of systemic immune‐inflammation index in asthma and NSAID‐exacerbated respiratory disease

Objective Asthma is a heterogeneous disease characterized by chronic progressive airway inflammation. Although the disease has numerous phenotypes, there are no practical biomarkers for distinguishing the phenotypes from one another. To address this challenge, we aimed to reveal whether the systemic immune‐inflammation index (SII), an important indicator of systemic inflammation and prognosis in various malignancies and vasculitis, can be used for distinguishing between asthma and NSAID‐exacerbated respiratory disease (NERD). Methods The study enrolled 105 patients (asthma: n = 69; NERD: n = 36). SII was calculated using the formula of neutrophil X platelet/lymphocyte number. Major risk factors, namely ACT score, eosinophil level, total IgE level, N‐L ratio (NLR), P‐L ratio (PLR), and SII, were evaluated by logistic regression analysis. Results No significant differences were found between the clinical features of the two study groups. Patients with an SII value ≥895.6 had a probability of having NERD with a sensitivity of 30.56%, whereas those with a lower SII had a probability of having asthma with a sensitivity of 92.65%. In the logistic regression analysis, no risk factor was determined for identifying asthma or NERD. The N‐L ratio was found to be the risk factor affecting categorized SII (OR = 264.2, 95% CI 9.9–7046.5, P  = 0.001). Conclusion This is the first study to evaluate SII as a tool for differentiating asthma phenotypes. The presence of SII below the cutoff value can help exclude the diagnosis of NERD. There is a need for large‐scale prospective studies to compare different phenotypes and determine the optimal cutoff value.