NITRITE LEVELS IN BREATH CONDENSATE OF PATIENTS WITH CYSTIC-FIBROSIS IS ELEVATED IN CONTRAST TO EXHALED NITRIC-OXIDE

Background-Nitric oxide (NO) leased by activated macrophages, neutroph ils, and stimulated bronchial epithelial cells. Exhaled NO has been sh own to be increased in patients with asthma and has been put forward a s a marker of airways inflammation. However, we have found that exhale d NO is not raised in patients with cystic fibrosis, even during infec tive pulmonary exacerbation. One reason for this may be that excess ai rway secretions may prevent diffusion of gaseous NO into the airway lu men. We hypothesised that exhaled NO may not reflect total NO producti on in chronically suppurative airways and investigated nitrite as anot her marker of NO production. Methods-Breath condensate nitrite concent ration and exhaled NO levels were measured in 21 clinically stable pat ients with cystic fibrosis of mean age 26 years and mean FEV1 57% and 12 healthy normal volunteers of mean age 31 years. Breath condensate w as collected with a validated method which excluded saliva and nasal a ir contamination and nitrite levels were measured using the Griess rea ction. Exhaled NO was measured using a sensitive chemiluminescence ana lyser (LR2000) at an exhalation rate of 250 ml/s. Fourteen patients wi th cystic fibrosis had circulating plasma leucocyte levels and differe ntial analysis performed on the day of breath collection. Results-Nitr ite levels were significantly higher in patients with cystic fibrosis than in normal subjects (median 1.93 mu M compared with 0.33 mu M). Th is correlated positively with circulating plasma leucocytes and neutro phils (r = 0.6). In contrast, exhaled NO values were not significantly different from the normal range (median 3.8 ppb vs 4.4 ppb). There wa s no correlation between breath condensate nitrite and lung function a nd between breath condensate nitrite and exhaled NO. Conclusions-Nitri te levels in breath condensate were raised in stable patients with cys tic fibrosis in contrast to exhaled NO. This suggests that nitrite lev els may be a more useful measure of NO production and possibly airways inflammation in suppurative airways and that exhaled NO may not refle ct total NO production.