Increased levels of fraction exhaled nitric oxide (FENO) have been found among individuals with atopic asthma and are believed to reflect on going airway inflammation. However, routine use of FENO in health care diagnosis and treatment is limited by the expense of the required equipment. Two offline methods are currently available for obtaining FENO namely, the American Thoracic Society (ATS) FENO 350cc/sec recommended method and the Dead Space Discard (DSD) FENO 50cc/sec kit method. However, there have not been published studies comparing the two techniques in the field. In the current study we sought to compare the FENO levels obtained by the ATS method and the DSD method and to investigate the utility of FENO levels in detecting inflammation is persons with diagnosed asthma.
Cross-sectional study. A convenient sample of 45 subjects ages 17 to 82 years, mean age 44.26 ± 16.71 years. There were 19 females and 26 males. Paired exhaled samples were collected from the subjects in triplicate using ATS and DSD techniques and analyzed offline using Sievers 280i Nitric Oxide Analyzer.
Comparison of the two methods was performed using correlations, regression analysis and ANOVA. 33.3% had health care provider diagnosed asthma, 8.9% had other respiratory problems, the remainders were healthy individuals with no known respiratory conditions; 11.1% were current cigarette smokers. FENO levels obtained by DSD technique were consistently higher than those obtained by the ATS technique. The two techniques were highly correlated r= 0.691, p<0.000, 2df and r2 = 0.48.
FENO levels obtained by the ATS and DSD technique are highly and positively correlated.
The DSD technique is well suited for field studies when replicate samples are to be collected from many subjects. Furthermore, the smaller bags are more cost efficient and easier to transport than the high flow bags.
Jamson Lwebuga-Mukasa, None.