Fluctuation of tissue eosinophils in chronic rhinosinusitis with nasal polyp.

Introduction: Tissue eosinophil count (TEC) is recommended for defining Type 2 chronic rhinosinusitis with nasal polyps (CRSwNP). TEC is usually assessed by a one-time polyp biopsy. Because TEC may change over time, its reliability for diagnosing type 2 CRSwNP has not been previously assessed. This study aims to explore whether TEC fluctuates across different time points.

Methods: Adult patients with CRSwNP were prospectively recruited at Rajavithi Hospital, Thailand. Participants who had used any form of steroids within 4 weeks were excluded. Polyps were taken for TEC evaluation upon recruitment and repeated at 3 and 6 months. Participants were assessed using the 22-items Sinonasal Outcome Test (SNOT-22), Lund-Kennedy endoscopic score (LKES), blood eosinophil count, and its percentage at each time point.

Results: Thirty-seven participants were enrolled. The medians (Quartiles 1-3) of TEC were 17 (4-53.5), 19 (5-47.5), and 21 (4.5-51) cells/high-powered field at 0, 3, and 6 months, respectively. Friedman's two-way analysis of variance showed no statistical differences across the three time points for TEC (p = 0.53), blood eosinophil counts (p = 0.61), blood eosinophil percentages (p = 0.23), SNOT-22 (p = 0.21), or LKES (p = 0.23). TEC significantly correlated with blood eosinophil counts at 0 and 3 months and with blood eosinophil percentages at 0, 3, and 6 months (all p < 0.05).

Conclusion: The study showed that TEC did not significantly fluctuate over time, aligning with blood eosinophil levels, SNOT-22, and LKES. This stability within the 6-month period supports the reliability of TEC from a single biopsy for clinical use in managing CRSwNP.