While cotinine is commonly used as a biomarker to validate self-reported smoking status, the selection of an optimal cotinine cutoff value for distinguishing true smokers from true nonsmokers shows a lack of standardization among studies. This review describes how the cutoff values have been derived, and explains the issues involved in the generalization of a cutoff value. In this study, we conducted an English-language literature search in PubMed using the keywords “cotinine” and “cutoff” or “self-reported” and “smoking status” and “validation” for the years 1985–2014. We obtained 104 articles, 32 of which provided (1) sensitivity and specificity of a cutoff value and (2) determination methods for the given cutoff value. We found that the saliva cotinine cutoff value range of 10–25 ng/mL, serum and urine cotinine cutoff of 10–20 ng/mL and 50–200 ng/mL, respectively, have been commonly used to validate self-reported smoking status using a 2 × 2 table or a receiver operating characteristics (ROC) curve. We also found that recent large population-based studies in the U.S. and UK reported lower cutoff values for cotinine in serum (3 ng/mL) and saliva (12 ng/mL), compared to the traditionally accepted ones (15 and 14 ng/mg, respectively).
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机译：虽然可替宁通常被用作验证自我报告吸烟状况的生物标志物，但是选择最佳可替宁截止值以区分真正吸烟者与真正非吸烟者显示出研究之间缺乏标准化。这篇综述描述了如何得出临界值，并解释了临界值的一般化所涉及的问题。在这项研究中，我们在PubMed中使用1985-2014年的关键词“烟碱”和“临界值”或“自我报告”，“吸烟状况”和“验证”对英语文献进行了搜索。我们获得了104篇文章，其中32篇提供了（1）临界值的敏感性和特异性，以及（2）给定临界值的测定方法。我们发现，唾液可替宁的截留值范围分别为10–25 ng / mL，血清和尿可替宁的截断范围分别为10–20 ng / mL和50–200 ng / mL，通常用于验证自我报告的吸烟状况使用2×2表格或接收器工作特性（ROC）曲线。我们还发现，最近在美国和英国进行的以人口为基础的研究报告，与传统上接受的15和14 ng / mL相比，血清（3 ng / mL）和唾液（12 ng / mL）中的可替宁的临界值较低。毫克）。
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