Fractional exhaled nitric oxide in healthy Thai adults and its association with pulmonary function

The fractional exhaled nitric oxide (FeNO) has been proposed to be a non-invasive marker of airway inflammation. There are no studies on normal FeNO values and its link to pulmonary function among Thais. This study determined the reference values of FeNO and its association with pulmonary function among healthy non-atopic, non-regular alcoholic and non-smoking Thai adults between 20 to 50 years of age. FeNO was measured using Quark NObreath in accordance with the American Thoracic Society guidelines and pulmonary function tests were performed in 18 males and 31 females. The mean FeNO level was 12.4 ± 6.2 ppb and the upper 95% confidence limit was 14.2 ppb in 49 healthy Thai adults (33.6 ± 9.36 yrs). Moreover, it was 13.4 ± 6.5 and 11.9 ± 6.1 ppb in male and female, respectively. Males had comparable FeNO levels, FVC (%pred), FEV 1 (%pred), FEF25-75% (%pred) and PEF (%pred) to females. Moreover, there was a negative correlation between FEF25-75% with FeNO level (r =-0.298, p=0.040) but not FVC or FEV1 or PEF. The present study provides normal FeNO values in Thai adults. They were similar to those of Caucasians and Japanese. Furthermore, the FeNO level was negatively linked to FEF25-75% indicating a small airway inflammation may be present in those with higher FeNO levels. Nevertheless, large random sample of Thais are required before integrating into clinical practice.