Effect of Preoperative Systemic Steroids on Tissue Eosinophils in CRSwNP: Meta-Analysis.

OBJECTIVE: Preoperative systemic corticosteroids are frequently used in chronic rhinosinusitis with nasal polyps (CRSwNP). This meta-analysis aimed to evaluate the effect of preoperative systemic steroids on tissue eosinophil count (TEC) in CRSwNP. DATA SOURCES: PubMed, EMBASE, and Cochrane Library. REVIEW METHODS: Systematic searches were conducted through March 2026 for studies assessing TEC following preoperative systemic steroids in adult CRSwNP patients. Eligible designs included randomized controlled trials, cohort studies, and pre-post studies. TEC was reported as cells per high-power field (TEC/HPF) or as a percentage of eosinophils among inflammatory cells (%TEC). Pooled mean differences (MD) were calculated using random-effects models. RESULTS: Seventeen studies (930 participants) were included, of which 13 were eligible for quantitative synthesis. Systemic steroids significantly reduced TEC/HPF (MD -36.57; 95% CI: -43.94 to -29.20) and %TEC (MD -18.14; 95% CI: -24.88 to -11.39). Reductions were consistent across steroid dose, duration, and concomitant intranasal steroid use. However, low dose (4.2-18.6 mg/day) given in ≤ 7-day regimens showed a non-significant reduction (MD -17.78; 95% CI: -62.62 to 27.05). Adverse events were not statistically different between the steroid and control groups (5.60% vs. 1.12%, odds ratio = 5.22, p = 0.12). No adverse events were reported in studies using low-dose or tapering regimens. CONCLUSION: Preoperative systemic corticosteroids significantly reduce TEC in CRSwNP, regardless of the quantifying method. This effect may interfere with histologic assessment when biopsy is taken intraoperatively. To avoid misinterpretation, clinicians may consider either withholding preoperative systemic corticosteroids, using a less suppressive regimen, or obtaining a biopsy prior to steroid initiation. LEVEL OF EVIDENCE: N/A.