Blood Eosinophil Count is the Dominant Clinical Marker for type 2 Inflammatory Severity in CRSwNP

Objective: Severe type 2 eosinophilic chronic rhinosinusitis with nasal polyps (CRSwNP) is challenging to treat and susceptible to recurrence post-surgery. This study aimed to evaluate the relationship between clinical markers and tissue type 2 inflammatory severity in patients with CRSwNP. Methods: Adult patients who underwent endoscopic sinus surgery for bilateral CRSwNP were prospectively enrolled. Tissue eosinophil count (TEC) was evaluated. Expression levels of type 2 cytokines, including IL-5 and IL-13, in nasal polyps were determined using real-time PCR. Correlations between clinical markers and tissue type 2 inflammation were also assessed. Results: In total, 150 participants were recruited. Ninety-five (63.3%) exhibited type 2 eosinophilic CRSwNP defined by TEC ≥10/high power field. Weak to moderate correlations were observed between clinical and tissue markers of type 2 inflammation. Among the clinical markers, blood eosinophil count (BEC) exhibited the highest correlation with tissue type 2 inflammatory severity, as determined by TEC, IL-5, and IL-13 expression levels in nasal polyps. Comorbid asthma, nonsmoking status, ethmoid/maxillary sinuses (E/M) ratio, and BEC were significant predictors of eosinophilic CRSwNP in the regression analysis. Conclusions: BEC, a dominant clinical marker, exhibits the highest correlation with tissue type 2 inflammatory severity, as determined by TEC, IL-5, and IL-13 in nasal polyps. Comorbid asthma, nonsmoking status, E/M ratio, and BEC were significant predictors of eosinophilic CRSwNP. This could help clinicians better evaluate the severity of type 2 inflammation in patients with CRSwNP and provide optimal therapeutic strategies. Level of Evidence: 4 Laryngoscope, 135:1326–1334, 2025.