Peripheral blood eosinophils as an adjunctive biomarker for eosinophilic otitis media: Supporting the validity of current diagnostic criteria

Objective Eosinophilic otitis media (EOM) is recognized as a type 2 inflammatory airway disease closely associated with bronchial asthma and chronic rhinosinusitis with nasal polyps (CRSwNP). Although peripheral blood eosinophils are established biomarkers of type 2 inflammation, their clinical significance in EOM remains unclear. This study aimed to evaluate the diagnostic utility of peripheral blood eosinophil counts in EOM in relation to current diagnostic criteria. Methods This retrospective study included 64 patients with EOM and 69 patients with chronic perforated otitis media (COM) who underwent tympanoplasty as controls. Peripheral blood eosinophil counts at the initial visit were compared between the groups. The optimal cut-off value for diagnosing EOM was determined using receiver operating characteristic (ROC) curve analysis. In addition, associations between eosinophil counts and clinical features were analyzed in the EOM group. Results The mean eosinophil percentage and absolute count were significantly higher in the EOM group than in the COM group (8.6% vs. 2.6% and 543/μL vs. 140/μL, respectively; P < 0.001). The optimal cut-off value for diagnosing EOM was > 249/μL (sensitivity: 85.7%, specificity: 79.2%, odds ratio: 22.9). In patients with EOM, higher eosinophil counts were significantly associated with perennial allergen-specific immunoglobulin E (IgE) positivity and the presence of nasal polyposis. However, eosinophil counts were not significantly correlated with middle ear findings, disease severity, or imaging scores. Conclusion Peripheral blood eosinophil counts > 249/μL may serve as an adjunctive biomarker to current diagnostic criteria for EOM. These levels do not appear to reflect local disease activity but rather indicate underlying systemic type 2 inflammation. The findings support the validity of current diagnostic criteria that incorporate comorbid type 2 inflammatory diseases, such as bronchial asthma and CRSwNP.