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

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. Thirty-three consecutive patients with CRSwNP underwent nasal cytology sampling 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. 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). Nasal cytology is suitable tool for assessing local biomarkers of type-2 inflammation in CRSwNP.