Exhaled nitric oxide, nitrite/nitrate levels, allergy, rhinitis and asthma in the EGEA study

Although interest in biomarkers in the nitrate-nitrite-NO pathway has recently increased, associations between nitrite (NO2(-)) and nitrate (NO3(-)), and asthma, allergic sensitisation and rhinitis remain unclear. The study aimed to evaluate the associations between NO2(-)/NO3(-) and exhaled fraction of nitric oxide (FeNO) levels with asthma, allergic sensitisation and rhinitis. Plasma and exhaled breath condensate (EBC) NO2(-)/NO3(-) and FeNO levels were measured in 523 adults of the French Epidemiological study on Genetics and Environment of Asthma. Allergic sensitisation was defined by a positive skin prick test for at least one aeroallergen. Subjects were classified as non-sensitised, sensitised and as having allergic rhinitis. Plasma NO2 (-)/NO3(-) level was unrelated to any disease phenotypes. EBC NO2(-)/NO3(-) level was unrelated to any asthma phenotypes. EBC NO2(-)/NO3(-) and FeNO levels were correlated in sensitised subjects only (r = 0.21 ± 0.10, p=0.01). EBC NO2(-)/NO3(-) and FeNO levels were higher in sensitised than in non-sensitised subjects (adjusted geometric mean (95% CI): 2.36 (1.96-2.84) versus 1.72 (1.38-2.14) μmol per mg proteins, p=0.008; and 18.3 (16.7-20.0) versus 14.8 (13.3-16.5) ppb, p=0.0006, respectively), with gradual relationships from sensitised subjects to those with allergic rhinitis (p<0.0001). Results suggest that EBC NO2(-)/NO3(-) and FeNO levels may be considered as biological markers of intensity of allergic sensitisation and rhinitis.