Airborne nitric oxide and nasal cytology in patients with chronic rhinosinusitis and nasal polyps

Nitric oxide (NO) is involved in eosinophilic inflammation. The fraction of exhaled nitric oxide (FENO) is increased in chronic rhinosinutis with nasal polyps (CRSwNP), whereas nasal NO (nNO) is reduced in chronic rhinosinutis. Nasal cytology can detect eosinophilic inflammation in CRSwNP. We aimed to describe the baseline rhinocytological characteristics and NO (FENO and nNO) levels in patients with CRSwNP, and assess their possible correlations. This longitudinal study involved 37 consecutive adult outpatients with CRSwNP and 36 healthy controls. They underwent a complete clinical otolaryngological assessment, measurement of FENO and nNO levels, and nasal scraping in order to collect material for nasal cytology. Disease severity was evaluated by means of endoscopic and Lund-Mackay radiological scores. Median FENO level was higher (p <0.001) in CRSwNP (28.3 ppb, 95%CI 13.0-33.6 ppb) than in the controls (7.5 ppb, 95%CI 6.1-8.9 ppb). Median nNO levels were lower (255.7, 95%CI 199.7-311.6 vs 385.5, 95%CI 345.0-425.9 ppb; p <0.001), and were lower in the patients with severe endoscopic obstruction (p=0.05). Lund-Mackay scores positively correlated with median FENO levels (R=0.11; p=0.05), and inversely with median nNO levels (R=-0.31; p=0.04). Metachromatic nasal cytotypes were more prevalent among CRSwNP patients who had previously undergone surgery (p=0.05). The number of metachromatic elements in the patients with CRSwNP positively correlated with their median FENO levels (R=0.24; p=0.002). Our results confirm the dynamic interplay between the upper and lower airways in patients with CRSwNP. FENO/nNO and nasal cytology can be useful for detecting and monitoring nasal inflammation in CRSwNP.