Public Health Department, Basque Government, San Sebastian, Spain.
BMJ Open. 2013 Jan 24;3(1):e002034. doi: 10.1136/bmjopen-2012-002034.
To estimate the prevalence and factors associated with smoking and misclassification in pregnant women from INMA (INfancia y Medio Ambiente, Environment and Childhood) project, Spain, and to assess the optimal cut-offs for urinary cotinine (UC) that best distinguish daily and occasional smokers with varying levels of second-hand smoke (SHS) exposure.
We used logistic regression models to study the relationship between sociodemographic variables and self-reported smoking and misclassification (self-reported non-smokers with UC >50 ng/ml). Receiver operating characteristic (ROC) curves were used to calculate the optimal cut-off point for discriminating smokers. The cut-offs were also calculated after stratification among non-smokers by the number of sources of SHS exposure. The cut-off points used to discriminate smoking status were the level of UC given by Youden's index and for 50 and 100 ng/ml for daily smokers, or 25 and 50 ng/ml for occasional smokers.
At the third trimester of pregnancy, 2263 pregnant women of the INMA Project were interviewed between 2004 and 2008 and a urine sample was collected.
Prevalence of self-reported smokers at the third trimester of pregnancy was 18.5%, and another 3.9% misreported their smoking status. Variables associated with self-reported smoking and misreporting were similar, including born in Europe, educational level and exposure to SHS. The optimal cut-off was 82 ng/ml (95% CI 42 to 133), sensitivity 95.2% and specificity 96.6%. The area under the ROC curve was 0.986 (95% CI 0.982 to 0.990). The cut-offs varied according to the SHS exposure level being 42 (95% CI 27 to 57), 82 (95% CI 46 to 136) and 106 ng/ml (95% CI 58 to 227) for not being SHS exposed, exposed to one, and to two or more sources of SHS, respectively. The optimal cut-off for discriminating occasional smokers from non-smokers was 27 ng/ml (95% CI 11 to 43).
Prevalence of smoking during pregnancy in Spain remains high. UC is a reliable biomarker for classifying pregnant women according to their smoking status. However, cut-offs would differ based on baseline exposure to SHS.
估计 INMA（环境与儿童）项目中西班牙孕妇吸烟和分类错误的流行率和相关因素，并评估尿可替宁（UC）的最佳截断值，以最佳区分不同水平二手烟（SHS）暴露的每日吸烟者和偶尔吸烟者。
我们使用逻辑回归模型研究社会人口统计学变量与自我报告吸烟和分类错误（自我报告非吸烟者的 UC>50ng/ml）之间的关系。接收者操作特征（ROC）曲线用于计算区分吸烟者的最佳截断值。还在非吸烟者中按 SHS 暴露源数分层后计算了截断值。用于区分吸烟状况的截断值是 Youden 指数给出的 UC 水平，以及每日吸烟者的 50 和 100ng/ml，或偶尔吸烟者的 25 和 50ng/ml。
在妊娠晚期，2004 年至 2008 年间 INMA 项目的 2263 名孕妇接受了访谈，并采集了尿液样本。
妊娠晚期自我报告吸烟者的流行率为 18.5%，另有 3.9%的人错误报告了他们的吸烟状况。与自我报告吸烟和错误报告相关的变量相似，包括出生在欧洲、教育水平和暴露于 SHS。最佳截断值为 82ng/ml（95%CI 42 至 133），灵敏度为 95.2%，特异性为 96.6%。ROC 曲线下面积为 0.986（95%CI 0.982 至 0.990）。根据 SHS 暴露水平，截断值分别为 42ng/ml（95%CI 27 至 57）、82ng/ml（95%CI 46 至 136）和 106ng/ml（95%CI 58 至 227），分别为未暴露于 SHS、暴露于 1 个和 2 个或更多 SHS 源。区分偶尔吸烟者和非吸烟者的最佳截断值为 27ng/ml（95%CI 11 至 43）。
西班牙孕妇吸烟的流行率仍然很高。UC 是根据吸烟状况对孕妇进行分类的可靠生物标志物。然而，截断值将根据基线 SHS 暴露情况而有所不同。
