Cropsey Karen L, Trent Lindsay R, Clark Charles B, Stevens Erin N, Lahti Adrienne C, Hendricks Peter S
Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, Birmingham, AL;
Department of Psychology, University of Mississippi, Oxford, Mississippi;
Nicotine Tob Res. 2014 Oct;16(10):1348-55. doi: 10.1093/ntr/ntu085. Epub 2014 Jun 2.
Confirming abstinence during smoking cessation clinical trials is critical for determining treatment effectiveness. Several biological methods exist for verifying abstinence (e.g., exhaled carbon monoxide [CO], cotinine), and while cotinine provides a longer window of detection, it is not easily used in trials involving nicotine replacement therapy. The Society for Research on Nicotine and Tobacco's Subcommittee on Biochemical Verification cite 8-10 parts per million (ppm) for CO as a viable cutoff to determine abstinence; however, recent literature suggests this cutoff is likely too high and may overestimate the efficacy of treatment.
This study examined the relationship between CO and cotinine in a sample of 662 individuals participating in a smoking cessation clinical trial. A receiver operating characteristics curve was calculated to determine the percentage of false positives and false negatives at given CO levels when using cotinine as confirmation of abstinence. Differences were also examined across race and gender.
A CO cutoff of 3 ppm (97.1% correct classification) most accurately distinguished smokers from nonsmokers. This same cutoff was accurate for both racial and gender groups. The standard cutoffs of 8 ppm (14.0% misclassification of smokers as abstainers) and 10 ppm (20.6% misclassification of smokers as abstainers) produced very high false-negative rates and inaccurately identified a large part of the sample as being abstinent when their cotinine test identified them as still smoking.
It is recommended that researchers and clinicians adopt a more stringent CO cutoff in the range of 3-4 ppm when complete abstinence from smoking is the goal.
在戒烟临床试验中确认戒烟对于确定治疗效果至关重要。存在多种用于验证戒烟的生物学方法（例如，呼出一氧化碳[CO]、可替宁），虽然可替宁提供了更长的检测窗口期，但它在涉及尼古丁替代疗法的试验中不易使用。尼古丁与烟草研究协会生化验证小组委员会将8 - 10百万分之一（ppm）的CO作为确定戒烟的可行临界值；然而，最近的文献表明这个临界值可能过高，可能会高估治疗效果。
本研究在662名参与戒烟临床试验的个体样本中考察了CO与可替宁之间的关系。计算了受试者工作特征曲线，以确定在使用可替宁作为戒烟确认指标时，给定CO水平下的假阳性和假阴性百分比。还考察了不同种族和性别的差异。
3 ppm的CO临界值（正确分类率为97.1%）最准确地区分了吸烟者和非吸烟者。这个临界值在种族和性别组中都是准确的。8 ppm（将吸烟者误分类为戒烟者的比例为14.0%）和10 ppm（将吸烟者误分类为戒烟者的比例为20.6%）的标准临界值产生了非常高的假阴性率，并且当可替宁测试表明他们仍在吸烟时，不准确地将很大一部分样本确定为已戒烟。
建议当以完全戒烟为目标时，研究人员和临床医生采用3 - 4 ppm范围内更严格的CO临界值。
