Exhaled Carbon Monoxide Level as an Indicator of Smoking among Undergraduate Students in Bangkok Metropolis and Bangkok Metropolitan
Measurement of exhaled carbon monoxide (eCO) has been used to evaluate tobacco smoking with a range of eCO cut-off point depending on specific populations. Early initiation of smoking before 20 years of age has been associated with greater consumption, longer duration of smoking, and increased nicotine dependence, consequently, influencing smoking cessation. This study aimed to apply eCO test as a tool for smoke free environment campaign by examining baseline eCO levels, the sensitivity and specificity of eCO test, and optimal cut-off value for smoking assessment in samples of the undergraduate students. Total of 389 undergraduate students living in Bangkok Metropolis and Bangkok Metropolitan underwent a measurement of eCO levels and completed questionnaire-based interview seeking demographic information and details of exposure to tobacco smoke, smoking habits and smoking-related knowledge. Active smokers (n = 200) had significantly higher eCO levels than non-smokers (n = 138) and passive smokers (n = 51) [median (95% CI); 9.00 (8.00, 11.00) ppm vs 3.00 (3.00, 3.00) ppm vs 2.00 (2.00, 3.00) ppm, p < 0.001], respectively. The eCO level at ≥ 6 ppm was optimal cut-off value to classify smokers, with sensitivity of 76.50% and specificity of 96.38%. When excluding data of smokers with > 6-hour since last cigarette, sensitivity increased to 84.12%. Obviously, active smokers who desired to quit smoking (n = 123) had a significantly higher awareness scores than those who did not (n = 73) (4.02 ± 0.95 vs 3.14 ± 1.31, p < 0.001). In conclusion, eCO test with optimal cut-off at ≥ 6 ppm is an effective tool to validate smoking status among undergraduate students and raise the student’s awareness on adverse effect of smoking. The reliability of test increased if an individual smoked with ≤ 6-hour prior to test.
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