Combined Neutrophil-to-Lymphocyte Ratio and Serum Neutrophil Elastase: Is it an Emerging Marker of Asthma Prognosis?

Abstract

Background: Asthma is a chronic obstructive airway disease, associated with an altered leukocyte population in the airways as well as in blood circulation with dysregulated immune responses. Limited studies are available that suggest the role of neutrophils and their derived markers in asthma severity, however, no reports exist on the combined effect. Methods: To examine these markers' individual and combined influence, we recruited a total of 92 individuals, 60 asthmatics (30 mild and 30 moderate) and 32 nonasthmatic healthy controls from South India. Absolute neutrophil count (ANC) and neutrophil-to-lymphocyte ratio (NLR) were obtained from the complete blood count, and serum neutrophil elastase (sNE) was estimated through ELISA. Results: A significant variation in the means of ANC, NLR, and sNE was observed between asthma patients and healthy controls, whereas mild and moderate asthmatics demonstrated the difference in only neutrophil derivates (NLR and sNE). The receiver operating characteristic curve analysis revealed NLR as an excellent diagnostic marker (area under the curve [AUC] = 0.79, cutoff = 1.51, Sn = 95, Sp = 65.53, P = 0.0001), whereas sNE has an excellent diagnostic and prognostic capacity (AUC = 0.92, cutoff = 14.27, Sn = 81.67, Sp = 90.63, P = 0.0001 and AUC = 0.86, cutoff = 18.82, Sen = 80, Spe = 83.33, P = 0.0001). No correlation was noted between NLR and sNE, signifying their independent control on asthma severity. The additive influence of NLR and sNE was noted when analyzed together in a Combination of NLR and sNE (CNN). CNN-1 score exhibited a 5-fold and CNN-2 19-fold increased risk of asthma severity. Conclusion: Based on the present findings, it appears that CNN may emerge as a single predictive marker in asthma prognosis. This is the first study of its kind projecting the potentiality of CNN that needs to be tested in a large cohort as the limitation of the current study is the sample size.