Proving driving under the influence of cannabis (DUIC) is difficult. Establishing a biomarker of recent use to supplement behavioral observations may be a useful alternative strategy. We determined whether cannabinoid concentrations in blood, oral fluid (OF) or breath could identify use within the past 3 h—likely the period of the greatest impairment. In a randomized trial, 191 frequent (≥4/week) and occasional (<4/week) cannabis users smoked one cannabis (placebo [0.02%], or 5.9% or 13.4% Δ9-tetrahydrocannabinol [THC]) cigarette ad libitum. Blood, OF and breath samples were collected prior to and up to 6 h after smoking. Samples were analyzed for 10 cannabinoids in OF, 8 in blood and THC in breath. Frequent users had more residual THC in blood and were more likely to be categorized as ‘recently used’ prior to smoking; this did not occur in OF. Per se limits ranging from undetectable to 5 ng/mL THC in blood offered limited usefulness as biomarkers of recent use. Cannabinol (CBN, cutoff = 1 ng/mL) in blood offered 100% specificity but only 31.4% sensitivity, resulting in 100% positive predictive value (PPV) and 94.0% negative predictive value (NPV) at 4.3% prevalence; however, CBN may vary by cannabis chemovar. A 10 ng/mL THC cutoff in OF exhibited the overall highest performance to detect its use within 3 h (99.7% specificity, 82.4% sensitivity, 92.5% PPV and 99.2% NPV) but was still detectable in 23.2% of participants ∼4.4 h post-smoking, limiting specificity at later time points. OF THC may be a helpful indicator of recent cannabis intake, but this does not equate to impairment. Behavioral assessment of impairment is still required to determine DUIC. This study only involved cannabis inhalation, and additional research evaluating alternative routes of ingestion (i.e., oral) is needed.

中文翻译：

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最近大麻在血液、口腔液和呼吸中使用的生物标志物

证明在大麻（DUIC）影响下驾驶是困难的。建立最近使用的生物标志物来补充行为观察可能是一种有用的替代策略。我们确定了血液、口腔液 (OF) 或呼吸中的大麻素浓度是否可以识别过去 3 小时内的使用——可能是最大损害的时期。在一项随机试验中，191 名频繁（​​≥4/周）和偶尔（<4/周）大麻使用者随意吸食一种大麻（安慰剂 [0.02%]，或 5.9% 或 13.4% Δ9-四氢大麻酚 [THC]）香烟. 在吸烟前和吸烟后 6 小时收集血液、OF 和呼吸样本。分析样品中 OF 中的 10 种大麻素、血液中的 8 种和呼吸中的 THC。经常使用的人血液中残留的 THC 较多，并且更有可能在吸烟前被归类为“最近使用”；这在OF中没有发生。血液中从无法检测到 5 ng/mL THC 的本身限制作为最近使用的生物标志物提供了有限的有用性。血液中的大麻酚（CBN，截止值 = 1 ng/mL）具有 100% 的特异性，但敏感性仅为 31.4%，导致 100% 的阳性预测值（PPV）和 94.0% 的阴性预测值（NPV），患病率为 4.3%；但是，CBN 可能因大麻化学变种而异。OF 中的 10 ng/mL THC 截止值在 3 小时内检测到其使用的总体最高性能（99.7% 特异性，82.4% 灵敏度，92.5% PPV 和 99.2% NPV）但在 23.2% 的参与者中仍可检测到 ~4.4 小时吸烟后，在以后的时间点限制特异性。OF THC 可能是近期大麻摄入量的有用指标，但这并不等同于损害。仍然需要对损伤进行行为评估来确定 DUIC。