Reference Ranges for Exhaled Nitric Oxide Fraction in Healthy Japanese Adult Population

抄録

Background: The measurement of the exhaled nitric oxide fraction (FE_NO) is proposed as a useful marker of airway inflammation. In healthy adults, there have been a few studies of the reference ranges for FE_NO in Caucasians. A community study in other regions may reveal any possible ethnic differences in the FE_NO levels.
Methods: A total of 240 healthy adults aged between 18 to 74 years were recruited from four medical centers in Japan. Current smokers and subjects having a history of atopic disease were not included. FE_NO was measured using an online electrochemical nitric oxide analyzer according to the current guidelines. The reference ranges for FE_NO were estimated using two different statistical methods recommended by International Federation of Clinical Chemistry and Laboratory Medicine.
Results: The mean FE_NO was 16.9 ppb (parts per billion) with a 95% prediction interval (2.5 to 97.5 percentiles) of 6.5 to 35.0 ppb in healthy Japanese adults. Normality assumptions were met for the logarithm-transformed FE_NO. The geometric mean FE_NO was 15.4 ppb with a mean ± two standard deviations of 6.5 to 36.8 ppb. Age, gender, height, and past smoking history were not associated with the FE_NO levels.
Conclusions: The reference ranges for FE_NO in healthy Japanese adults were similar to those of Caucasians. It seems reasonable that the upper limit of FE_NO for healthy adults should be set at approximately 36.0 ppb irrespective of ethnic differences.