Effect of corticosteroids on tissue eosinophilia in chronic rhinosinusitis: a systematic review and meta-analysis

INTRODUCTION: This systematic review and meta-analysis evaluated the effect of oral corticosteroid (CS) treatment on tissue eosinophil count (EC) in chronic rhinosinusitis (CRS) patients. METHODOLOGY: A comprehensive database search identified 16 studies with 1,003 patients for the systematic review. Nine studies with 493 patients reporting mean tissue EC per high-power field (HPF) with 400x magnification were included in the meta- analysis. Within-subject (pre- vs. post CS treatment) and controlled comparisons (oral CS vs. no CS or topical CS) were analyzed. RESULTS: Results showed a significant reduction in tissue EC following oral CS treatment in both within-subject analyses and controlled trials. A similar effect was found when comparing oral vs. topical CS treatment. Meta-regression showed a significant negative association between cumulative CS dose and post-treatment EC/HPF. CONCLUSION: These findings provide strong evidence that oral CS significantly reduces tissue eosinophilia in CRS, including comparisons with topical CS. The effect was consistent across study designs and should be considered when assessing endotypes in CRS with nasal polyps.