A single system: two measurements of nitrogen oxide concentration in a nasal challenge test with an allergen

Introduction. Due to its high sensitivity and specificity, nasal allergen challenge (assessed using nitric oxide levels in exhaled air) occupies a special place among differential diagnostic tests for allergic rhinitis. Aim. The aim of this study was to assess the marker of inflammation (nitric oxide) in exhaled breath condensate in nasal allergen challenge (NAC) test. Materials and methods. Sixty subjects were recruited for the study: 30 patients diagnosed with an allergy to common environmental allergens and 30 healthy controls. The method applied in the study was the NAC with the use of a standardised 5000 SBU/MI allergen dose, monitored by measuring the concentration of nitric oxide in exhaled air (from the nose (nNO) and the bronchi (oNO)). Results. Measurements of the concentration of nitrogen oxide in the air exhaled from the respiratory system showed a complexity of reactions in the NAC, with clear differences between the group of subjects with allergic rhinitis and the group of healthy controls. In the early phase of the allergic reaction, nNO level decreased. At 4th hour after nasal allergen application, oNO level increased from 22.17 to 23.13 ppb in the group of patients with allergic rhinitis. A moderate correlation was found between the subjects' complaints measured using the VAS scale and: nNO before the NAC (r = 0.569, p < 0.05), at the 25th minute of the test (r = 0.464, p < 0.05) at the 4th hour of the test (r = 0.529, p < 0.05) and oNO in the first test (r = 0.295, p = 0.022) at the 45th minute of the test (r = 0.349, p = 0.006) and in the late phase of the allergic reaction (r = 0.356, p < 0.05). Conclusion. NAC with measurements of nNO and oNO concentration levels provide valuable information on the response of the respiratory system to nasal challenge tests.