Exhaled Carbon Monoxide Level and Smoking Status in Urban Khon Kaen Adults
Supaporn Chatrchaiwiwatana PhD*, Amornrat Ratanasiri PhD**
Affiliation : * Faculty of Dentistry, Khon Kaen University, Khon Kaen ** Faculty of Medicine, Khon Kaen University, Khon Kaen
Background : Recent data has shown that a great number of Thai adults as well as people worldwide have
died from smoking-related diseases. Measurements of exhaled carbon monoxide have been increasingly used
to evaluate smoking status and cutoff levels of exhaled carbon monoxide and have been widely reported
among other populations but not for the Thai people.
Objective : The purpose of the present research was to study the proper cutoff level for exhaled carbon monoxide
for detecting smoking status among urban Thai adults residing in Khon Kaen province, Thailand as well as to
study the effect of baseline characteristics in modifying the cutoff level of exhaled carbon monoxide.
Study
Results : Cross-sectional analytic study.
Material and Method: The present study employed existing data whereby the study subjects comprised a total
of 420 Thai adults, aged 15-70 years, residing in urban Khon Kaen province, Thailand during the year 2006.
The data was obtained through interview and exhaled carbon monoxide measurement. The analyses employed
descriptive, bivariate, and multivariable logistic regression.
Results : Findings from the final multivariable logistic regression model revealed good relation between
exhaled carbon monoxide levels and tobacco smoking status. Other variables in the model included age-
group and the interaction between exhaled carbon monoxide and age-group. Further analysis showed a
greater odds ratio in the older age-group, with the odds ratios (95% CI) being 2.50 (1.87, 3.34) and 1.46
(1.31, 1.63) in the older (41-70 years) and younger (15-40 years) age-groups, respectively. In addition,
proper cutoff of exhaled carbon monoxide for the older age-group was suggested as 7 ppm, while 8 ppm was
more appropriate for the younger age-group. Based on the findings, a baseline characteristic for age modified
cutoff level of carbon monoxide was established.
Conclusion : Differences in baseline characteristics should be considered in evaluating smoking status when
choosing the cutoff level of exhaled carbon monoxide for any population.
Keywords : Exhaled carbon monoxide, Tobacco smoking, Baseline characteristic, Age
