Department of Pathology, University of Utah Health Sciences Center, Salt Lake City, UT.
ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, UT.
J Appl Lab Med. 2020 May 1;5(3):569-574. doi: 10.1093/jalm/jfaa020.
The psychoactive component of cannabis, tetrahydrocannabinol (THC), is one of many cannabinoids present in the plant. Since cannabinoids have extensive structural similarity, it is important to be aware of potential cross-reactivity with immunoassays designed to detect THC metabolite. This is especially important as cannabinoid products are increasingly marketed as legal supplements. The objective of this study was to assess the cross-reactivity of 2 commercial immunoassays designed to detect THC metabolite with 4 cannabinoids: cannabidiol, cannabinol, cannabichromene, and cannabigerol.
Deidentified residual patient urine samples that tested negative for THC metabolite on initial testing were pooled and fortified with the above compounds to detect cross-reactivity. We next tested a range of CBN concentrations to determine what concentration of CBN was required to trigger a positive immunoassay result. Finally, we tested whether CBN has an additive effect with THC in the immunoassay by adding CBN to 21 samples weakly positive for THC by a mass spectrometry method but negative by the EMIT II Plus immunoassay.
Both the EMIT II Plus assay and the Microgenics MultiGent assay demonstrated cross-reactivity with CBN. For the EMIT II Plus assay, about 5-fold more CBN than THC metabolite was required to produce an assay signal equivalent to the cutoff concentration, and CBN displayed an additive effect with THC metabolite. For the Microgenics assay, 20-fold more CBN than THC metabolite was required to cross the cutoff concentration.
These data may help guide the need for confirmatory testing when results of THC metabolite testing by immunoassay are inconsistent with expectations.
大麻的精神活性成分四氢大麻酚（THC）是植物中存在的众多大麻素之一。由于大麻素具有广泛的结构相似性，因此了解与设计用于检测 THC 代谢物的免疫分析物潜在交叉反应性非常重要。随着大麻素产品越来越多地作为合法补充剂推向市场，这一点尤为重要。本研究的目的是评估两种商业免疫分析物检测 THC 代谢物的交叉反应性与 4 种大麻素：大麻二酚、大麻酚、大麻色烯和大麻二醇。
将初始检测结果为 THC 代谢物阴性的患者尿液残留样本进行去识别，并混合这些化合物进行检测，以评估交叉反应性。接下来，我们测试了一系列 CBN 浓度，以确定触发免疫分析阳性所需的 CBN 浓度。最后，我们通过向通过质谱法检测呈弱阳性但 EMIT II Plus 免疫分析法呈阴性的 21 个 THC 样本中添加 CBN，来测试 CBN 与 THC 在免疫分析中的相加作用。
EMIT II Plus 分析法和 Microgenics MultiGent 分析法均显示出与 CBN 的交叉反应性。对于 EMIT II Plus 分析法，产生与截止浓度相当的分析信号所需的 CBN 量大约是 THC 代谢物的 5 倍，并且 CBN 与 THC 代谢物具有相加作用。对于 Microgenics 分析法，需要 20 倍于 THC 代谢物的 CBN 才能越过截止浓度。
当免疫分析检测 THC 代谢物的结果与预期不一致时，这些数据可能有助于指导进行确认性检测的必要性。
