Validation of nitrite and nitrate measurements in exhaled breath condensate.
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.


OBJECTIVE
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) micromol/l] and patients [4.6 (2.6-7.3) and 8.7 (3.2-23.8) micromol/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 degrees 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.
Department of Pediatrics, Charles University in Prague, Faculty of Medicine in Hradec Králové, Prague, Czech Republic.
Jirina
J
Chladkova
Irena
I
Krcmova
Jaroslav
J
Chladek
Petr
P
Cap
Stanislav
S
Micuda
Yvona
Y
Hanzalkova
D000328:Adult; D001249:Asthma / Q000378:metabolism; D001944:Breath Tests / Q000295:instrumentation / Q000379:methods*; D002845:Chromatography; D018592:Cross-Over Studies; D045853:Exhalation; D005260:Female; D005470:Fluorometry; D006801:Humans; D008168:Lung / Q000378:metabolism*; D008297:Male; D009566:Nitrates / Q000378:metabolism*; D009573:Nitrites / Q000378:metabolism*; D013048:Specimen Handling
D009566:Nitrates; D009573:Nitrites