Nasal nitric oxide concentration in suspected chronic rhinosinusitis

Background: The role that nasal nitric oxide (nNO) plays in sinonasal diseases is increasingly appreciated. Objective: To test the diagnostic value of measuring nNO levels in a symptomatic population undergoing evaluation for potential chronic rhinosinusitis (CRS). Methods: Of the patients referred to an outpatient allergy clinic for persistent nasal symptoms, those reporting nasal blockage plus 1 or more additional symptoms (discolored discharge, anterior or postnasal drip, facial pain or pressure, and reduction or loss of smell) were categorized as having CRS according to sinus computed tomography scores, with (CRSwNP) and without (CRSsNP) nasal polyps on the basis of endoscopic signs. All the included patients underwent nNO measurement and skin prick tests for common inhalant allergens. Healthy individuals served as controls for nNO measurement. Results: Levels of nNO were significantly lower in patients with CRSwNP (median, 340 ppb; 25th-75th percentile, 145-390 ppb) compared with patients with CRSsNP (762 ppb; 620-1,013 ppb), patients without CRS (917 ppb; 647-1,159 ppb), and controls (843 ppb; 762-962 ppb) (P < .001). Low values of nNO separated very well patients with CRSwNP, and the nNO cutoff value of less than 442 ppb was associated with the best combination of specificity (91%) and sensitivity (87%), resulting in a negative predictive value of 91% and a positive predictive value of 87%. A significant inverse relationship was observed between nNO level and sinus computed tomogaphy score (r(2) = -0.39, P <.001). Conclusion: Testing for nNO is highly predictive of CRSwNP in a selected population of patients with symptoms suggestive of CRS.