Fluctuation of tissue eosinophils in chronic rhinosinusitis with nasal polyp

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.

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.

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).

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.