Sombutpiboonphon K.Snidvongs K.Lawpoolsri S.Chotikawichean N.Kowatanamongkon P.Mongkolkul K.Chitsuthipakorn W.Mahidol University2024-12-222024-12-222024-01-01International Forum of Allergy and Rhinology (2024)20426976https://repository.li.mahidol.ac.th/handle/20.500.14594/102469Introduction: 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.MedicineArticleSCOPUS10.1002/alr.234942-s2.0-8521219666120426984