Nasal cytology as a reliable non-invasive procedure to phenotype patients with type 2 chronic rhinosinusitis with nasal polyps

Background: The identification of type-2 inflammation in patients with chronic rhinosinusitis with nasal polyps (CRSwNP) acquires a crucial role in the endotypization needed for selecting patients for biological drugs targeting type-2 inflammation: to date, the parameters used include systemic and histological biomarkers. The aim of this study was to investigate whether nasal cytology could identify type-2 inflammation in patients with CRSwNP.Methodology: Thirty-three consecutive patients with CRSwNP underwent nasal cytology sam-pling at the level of the lower nasal turbinate, and of the polypoid tissue, and surgical polyp tissue sample was collected. The cellularity of the 3 collected samples were compared.Results: Mean nasal polyp tissue, nasal polyps cytology and inferior turbinate cytology eosinophils counts were 43.7 + 39.6 cells/HPF, 32.8 + 44.7 cells/HPF and 27.6 + 58.0 cells/HPF respectively with inferior turbinate cytology eosinophils significantly lower than nasal polyp tissue count (p = 0.007). Both mean nasal polyps cytology eosinophils and mean inferior turbinate cytology eosinophils were significantly higher in patients with type-2 CRSwNP (52.5 + 67.0 cells/HPF vs 12.2 + 17.3 cells/HPF, p = 0.012, and 32.0 + 62.1 cells/HPF vs 2.9 + 2.9 cells/HPF, p = 0.020 respectively).Conclusions: Nasal cytology is suitable tool for assessing local biomarkers of type-2 inflammation in CRSwNP.