Validation of Nitrite and Nitrate Measurements in Exhaled Breath Condensate

Abstract

Background: Inflammatory markers in exhaled breath condensate (EBC) are investigated as a non-invasive approach to monitoring of inflammation in the respiratory tract. EBC concentrations of nitrite and nitrate, the stable end products of oxidative metabolism of nitric oxide, are increased in patients with asthma, especially during acute exacerbations. Objectives: To examine methodological aspects of nitrite and nitrate measurements in EBC such as sample collection, storage and analysis. Methods: In a randomized study, EBC was collected twice within 1 h (with and without a nose clip) in 20 healthy adults and 20 patients with well-controlled asthma and no symptoms of allergic rhinitis. Nitrite and nitrate were assayed by ionex chromatography and fluorimetrically after derivatization with diaminonaphthalene. Results: The geometric mean [exp (mean ± SD)] EBC levels of nitrite and nitrate in healthy subjects [4.3 (3.0–6.1) and 11.0 (5.3–22.7) µmol/l] and patients [4.6 (2.6–7.3) and 8.7 (3.2–23.8) µmol/l] did not differ (p = 0.13). Wearing a nose clip (p = 0.3) did not influence nitrite and nitrate concentrations. The mean intra-subject %CVs of EBC concentrations of nitrite were 26 and 21% in healthy subjects and patients, while those of nitrate achieved 49 and 88%, respectively. Conclusions: Ionex chromatography of nitrite and nitrate requires no sample pretreatment and provides comparable results as a more laborious diaminonaphthalene method. EBC samples should be kept cold (8°C) and analyzed for nitrite and nitrate within 24 h of collection or stored in the freezer and thawed preferably only once. Wearing a nose clip during EBC collection has no influence on nitrite and nitrate concentrations. Short-term repeatability of nitrite and nitrate measurements was worse compared to published data on exhaled nitric oxide.

Chlorine in Breath Condensate – A Measure of Airway Affection in Pollinosis?

“…EBC was collected while using a noseclip as recommended by the ATS/ERS task group [27]. Lack of nasal contamination of nitrite/nitrate has recently been reported [28] and we propose that contamination of saliva and/or nasal discharge seems unlikely as a source of major error in our study. Contamination by saliva, nasal discharge or even by handling of samples and collection tubes is a potential risk in evaluation of extremely low contents of biomarkers in EBC.…”

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

“…Both epidemiological and clinical studies have shown increased level of FeNO in children and adults with asthma, and positive associations between FeNO and allergic sensitisation are consistent over the studies, regardless of rhinitis or asthma [4]. Studies on associations between NO 2 -and NO 3 -levels with asthma, allergy or rhinitis have led to more conflicting results both in adults and children [5][6][7][8][9][10][11][12][13][14][15][16][17]. Until now, none of these studies has simultaneously performed measurements of EBC NO 2 -/NO 3 -and FeNO levels in the same subjects.…”

Early Effect of Tidal Volume on Lung Injury Biomarkers in Surgical Patients With Healthy Lungs

“…Nitric oxide metabolites-All samples were maintained frozen until analysis to minimize stability changes from freezing/thawing cycles and ambient contamination 40 . The collection and storage manipulation were strict because of concerns of nitric oxide metabolites instability and contamination from ambient air 41,42 .…”