Tissue eosinophils and mucous inflammatory cytokines for the evaluation of olfactory recovery after endoscopic sinus surgery in patients with nasal polyposis

The etiologies of chronic rhinosinusitis with nasal polyps (CRSwNP)-associated olfactory dysfunction have several potentially overlapping hypotheses. Understanding the association of tissue eosinophils and mucous inflammatory cytokines with olfactory function and identifying predictors of olfactory outcomes in patients with nasal polyposis after surgery is fundamental for future clinical care and research. Eighty-five patients who underwent endoscopic surgery for nasal polyposis were enrolled in this study. Olfactory measurements were performed before surgery and 3–6 months after surgery using a T&T olfactometer. Baseline characteristics of CRSwNP patients were collected, and Spearman's rho correlation was performed to assess the association of olfactory function with tissue eosinophils and mucous inflammatory cytokines. A multivariate logistic regression model was used to assess the independent predictors of olfactory outcomes after surgery. Here, 85 CRSwNP patients, including 25 patients without olfactory disorder and 60 patients with hypo-anosmia, were evaluated. Of the 60 patients with preoperative hypo-anosmia, 22 did not have improved olfactory function, and 38 demonstrated normal olfactory function after surgery based on the T&T olfactometer results. The levels of tissue eosinophil, interleukin-5 (IL-5), IL-13, eotaxin-3, and periostin in the preoperative hypo-anosmia group were higher than those in the preoperative normosmia group. Tissue eosinophil count, IL-5, and periostin levels in patients without olfactory improvement were higher than those in patients with olfactory improvement. The tissue eosinophil count, blood eosinophil count, and nasal mucus levels of IL-5, eotaxin-3, and periostin were significantly correlated with olfactory function in all patients with CRSwNP. The IL-5 level remained a strong predictor of poor olfactory outcomes after surgery. Both tissue eosinophils and mucous inflammatory cytokines, including IL-5, IL-13, eotaxin-3, and periostin, may contribute to the pathogenesis of CRSwNP-associated olfactory dysfunction. Higher IL-5 levels are associated with a lower chance of olfactory function recovery after each surgical revision.