Centre for Clinical Epidemiology, Lady Davis Institute, Jewish General Hospital/McGill University, Montreal, QC, Canada.
Faculty of Medicine and Health Sciences, McGill University, Montreal, QC, Canada.
BMJ Open. 2023 Oct 13;13(10):e071099. doi: 10.1136/bmjopen-2022-071099.
Expired carbon monoxide (ECO) is often used in smoking cessation trials to biochemically validate self-reported smoking status. The optimal ECO threshold to distinguish individuals who smoke from those who do not is debated.
The data from the 'Evaluating the Efficacy of E-Cigarette use for Smoking Cessation (E3) Trial' were used; the E3 trial was a randomised controlled trial that examined e-cigarettes efficacy for smoking cessation.
Participants were recruited from 17 Canadian sites across 4 provinces.
This substudy included data from participants who returned for at least one of the clinical visits at week 4 (291), 12 (257) or 24 (218) and provided both self-reported smoking status and ECO measures. Analyses were based on 766 paired measures (ie, self-reported smoking status with corresponding ECO).
The ability of ECO measurements to discriminate between adults who reported smoking and those who reported abstinence varied with the threshold used. ECO thresholds of 6, 7, 8 and 9 parts per million (ppm) yielded the greatest area under the receiver operating characteristic curve (0.84). These thresholds produced sensitivities of 84%, 82%, 78% and 76% and specificities of 84%, 87%, 90% and 91%, respectively. However, at a threshold of 6 ppm, intersecting sensitivity (84%) and specificity (84%) were maximised with respect to each other. Biochemical validation had the highest agreement with self-report at an ECO threshold of 6 ppm (κ=0.57; 95% CI, 0.51 to 0.64).
The classification of participants' smoking status depends on the ECO threshold used for biochemical validation. We recommend that future smoking cessation trial investigators analyse and report the impact that varying ECO thresholds has on trial results.
NCT02417467.
内源性一氧化碳（ECO）常用于戒烟试验，以生化方法验证自我报告的吸烟状态。目前，用于区分吸烟者和非吸烟者的最佳 ECO 阈值仍存在争议。
使用“评估电子烟戒烟疗效（E3）试验”的数据；E3 试验是一项随机对照试验，研究电子烟戒烟的疗效。
参与者招募自加拿大 4 个省的 17 个地点。
本亚组研究包括至少参加第 4 周（291 人）、第 12 周（257 人）或第 24 周（218 人）临床访视且同时提供自我报告的吸烟状态和 ECO 测量值的参与者的数据。分析基于 766 对测量值（即，自我报告的吸烟状态与相应的 ECO）。
ECO 测量值区分报告吸烟和报告戒烟的成年人的能力随阈值的变化而变化。ECO 阈值为 6、7、8 和 9ppm 时，受试者工作特征曲线下面积最大（0.84）。这些阈值的灵敏度分别为 84%、82%、78%和 76%，特异性分别为 84%、87%、90%和 91%。然而，在 6ppm 的阈值下，灵敏度（84%）和特异性（84%）相交，彼此之间达到最大化。ECO 阈值为 6ppm 时，生化验证与自我报告的一致性最高（κ=0.57；95%CI，0.51 至 0.64）。
参与者吸烟状态的分类取决于用于生化验证的 ECO 阈值。我们建议未来的戒烟试验研究人员分析和报告不同 ECO 阈值对试验结果的影响。
NCT02417467。
