Measurement of fractional exhaled nitric oxide (FENO) levels have been used to aid diagnosis and monitoring of asthma in both adults and children. The current cutoff level of FENO in healthy adults was based on studies done in Caucasians. Grasemann and coworkers previously showed lower FENO in females due to genotypic differences. Our study examined the ethnic influences on FENO in non-asthmatics, according to gender.
Healthy non-asthmatic volunteers had FENO measured online using NIOX(R) (Aerocine AB, Sweden) according to American Thoracic Society (ATS) guidelines (1999). Log transformation of FENO was carried out. Comparison was made by t-test and ANOVA using SPSS for Windows (version 9).
We studied 72 volunteers: 35 Chinese (12 females), 13 Caucasians (5 females), and 24 Malays (11 females). ANOVA showed that FENO was significantly different between races (p=0.040). Geometric mean and SD of FENO in Caucasians (17.9,1.4 ppb) was significantly lower than Chinese (30.6,2.1 ppb, p=0.015) or Malays (26.8,1.8 ppb, p=0.032). When stratified according to gender, FENO was significantly different among males (p=0.003). Caucasians males (16.6,1.5 ppb) had significantly lower FENO compared to Chinese (39.9,1.9 ppb, p=0.001) or Malays (36.8,1.8 ppb, p=0.003). FENO did not differ between the ethnic groups in females (p=0.977). Caucasians (20.1,1.1 ppb), Chinese (18.4,1.9 ppb), Malays (18.4,1.5 ppb).
Our results showed that non-asthmatic Caucasians had significantly lower FENO levels compared to Chinese and Malays. This difference was found to be due to ethnic variations among males rather than females.
Ethnic and gender factors can markedly influence FENO, and published normal FENO levels in Caucasians should not be extrapolated to other ethnic groups.
T.K. Augustine, None.