Predictive value of blood eosinophil count and serum total immunoglobulin E for type 2 chronic rhinosinusitis according to allergic sensitization status.

PURPOSE: This study aimed to evaluate the diagnostic performance of blood eosinophil count (BEC) and serum total IgE for type 2 (T2) chronic rhinosinusitis (CRS) and to determine whether their performance is affected by allergic sensitization or other patient characteristics. METHODS: Data from 177 patients with CRS who underwent endoscopic sinus surgery were analyzed. T2 CRS was defined as tissue eosinophil count (TEC) ≥ 10 eosinophils/high-power field. Correlations between BEC, blood eosinophil percentage (BEP), serum total IgE, and TEC were assessed. The diagnostic performance for T2 CRS was evaluated using receiver operating characteristic (ROC) curve analysis. Patients were divided into allergic and non-allergic groups according to allergic sensitization, and subgroup analyses were conducted. RESULTS: BEC and BEP, but not serum total IgE, were positively correlated with TEC, regardless of allergic sensitization. Consistently, the area under the curve (AUC) values for BEC in ROC analyses were comparable across the total cohort and the allergic and non-allergic groups and remained stable across different histologic definitions of T2 CRS. Serum total IgE exhibited significantly lower AUC values than BEC, with values generally lower in the non-allergic group. Youden index-based optimal cutoff values for BEC clustered around 220-230/µL, exceeding the conventional threshold of 150/µL. CONCLUSION: The findings support the use of BEC as a preferred surrogate marker for tissue eosinophilia-defined T2 CRS regardless of allergic sensitization, and suggest that a modest upward revision of the BEC cutoff may be warranted. Serum total IgE demonstrated limited diagnostic value for tissue eosinophilia-defined T2 CRS, particularly in the non-allergic group.