Department of Chemical Pathology, University of Pretoria/National Health Laboratory Service, Tshwane Academic Division, South Africa.
Ann Clin Biochem. 2012 Mar;49(Pt 2):194-6. doi: 10.1258/acb.2011.011118. Epub 2011 Nov 8.
It has been known for some time that the antiretroviral drug, efavirenz (EFV), cross-reacts in urine immunoassays for tetrahydrocannabinol (THC). Because published studies investigating this phenomenon are limited, cross-reactivity information for several immunoassays is lacking. Reports of possible false-positive THC results from clinicians conducting workplace testing prompted us to investigate cross-reactivity for assays frequently employed in our own setting. In light of the potentially deleterious consequences of misclassification, information about EFV cross-reactivity should be included in product information to facilitate interpretation of results and assay selection.
Random urine samples from 30 patients on EFV therapy were analysed for THC metabolites by two near-testing devices (THC One Step Marijuana and Rapid Response(®) Drugs of Abuse Test Strips) and two automated immunoassays (Roche Diagnostics Cannabinoids II and Beckman Coulter SYNCHRON(®) Systems THC2). THC confirmatory testing was performed by gas chromatography-mass spectrometry (GC-MS).
GC-MS failed to detect THC metabolites in any of the samples, as did three of the four immunoassays. However, the Rapid Response(®) test strips yielded positive results in 28 out of 30 samples, which could be reversed on re-testing after sample pretreatment with glucuronidase.
Our study supports previous findings that interference is attributable to a glucuronidated EFV metabolite. We postulate that cross-reactivity is influenced by the composition of immunogens used to elicit anti-THC antibodies. Since access to such information is restricted, contributions from scientists in the antibody industry may be enlightening.
抗逆转录病毒药物依非韦伦（EFV）会与尿液免疫分析法中的四氢大麻酚（THC）发生交叉反应，这一点已经众所周知。由于目前发表的研究该现象的文献有限，因此缺乏几种免疫分析法的交叉反应信息。由于临床医生在进行工作场所检测时可能会报告出现假阳性的 THC 结果，因此促使我们调查了在我们自己的检测环境中常用的几种免疫分析法的交叉反应。鉴于分类错误可能产生的潜在有害后果，应在产品信息中提供有关 EFV 交叉反应的信息，以方便对结果和分析选择进行解读。
对正在接受 EFV 治疗的 30 名患者的随机尿液样本进行了两种接近检测的设备（THC One Step Marijuana 和 Rapid Response(®) Drugs of Abuse Test Strips）和两种自动化免疫分析法（罗氏诊断公司的大麻素 II 和贝克曼库尔特 SYNCHRON(®) Systems THC2）的 THC 代谢物分析。采用气相色谱-质谱法（GC-MS）进行 THC 确证性检测。
GC-MS 未能在任何样本中检测到 THC 代谢物，四种免疫分析法中有三种也是如此。然而，Rapid Response(®) 测试条在 30 个样本中的 28 个样本中产生了阳性结果，这些结果可以通过在样本预处理后用葡萄糖醛酸酶重新检测而得到逆转。
我们的研究支持了之前的研究结果，即干扰归因于结合型 EFV 代谢物。我们推测，交叉反应受用于引发抗 THC 抗体的免疫原组成的影响。由于无法获得此类信息，因此抗体行业的科学家的贡献可能会有启发性。
