Poon S, Gareri J, Walasek P, Koren G
The Motherisk Program, Division of Clinical Pharmacology and Toxicology, The Department of Pediatrics, The Hospital for Sick Children, Toronto, ON, Canada; Department of Pharmacology and Toxicology, University of Toronto, Toronto, ON, Canada.
The Motherisk Program, Division of Clinical Pharmacology and Toxicology, The Department of Pediatrics, The Hospital for Sick Children, Toronto, ON, Canada.
Forensic Sci Int. 2014 Aug;241:150-4. doi: 10.1016/j.forsciint.2014.05.019. Epub 2014 Jun 13.
In hair analysis, cocaine (COC) and its metabolites have been studied relatively extensively with a consistent focus of distinguishing active drug use and excluding external contamination. Although quantitative cut-offs using major metabolite, benzolecgonine (BE), in hair have been proposed to distinguish likely active use from passive exposure, exogenously formed BE may result in false positive tests. Hence, the presence of less commonly detected COC metabolite, norcocaine (NCOC), may be useful in increasing certainty of illicit COC use and evaluating likelihood of environmental contamination. The objective of the present study was to observe the pattern of NCOC detection in a clinical population of suspected users and evaluate the possible role of NCOC in distinguishing systemic exposure from external contamination to COC and assessing intensity of cocaine use. Hair samples collected between January 2011 and May 2013 from the Motherisk Laboratory were analyzed by GC-MS for the presence of COC, BE, and NCOC. NCOC positivity rates (%) for various COC concentration ranges as well as sensitivity, specificity, positive predictive value, and negative predictive values of NCOC as a biomarker of different COC use profiles was calculated. The rate of NCOC positivity (%) within COC concentration ranges (ng/mg) 0.13-0.4 (above LOD, below LOQ), 0.4-3, 3-6, 6-10, 10-14, >14 were 0.26, 4.15, 29.63, 55.85, 80.37, and 94.02, respectively; p<0.0001 for all positivity comparisons between ranges. These results were used to determine a COC cut-off concentration for differing levels of COC use. The presence of NCOC above the LOD of 0.13 ng/mg predicted COC concentrations exceeding 14.00 ng/mg, with sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 94.0%, 87.9%, 41.5%, and 99.4%, respectively. The presence NCOC above the LOD of 0.13 ng/mg predicted COC concentrations exceeding the 75th percentile, with sensitivity, specificity, PPV, and NPV of 76.6%, 94.7%, 74.7%, and 95.2%, respectively. Despite an inability to definitively rule out external contamination, the presence of NCOC in hair is strongly associated with elevated COC levels and performs as a highly specific surrogate marker for frequent/intensive cocaine use and highly sensitive marker for intensive/daily use of cocaine.
在毛发分析中，可卡因（COC）及其代谢物已得到较为广泛的研究，始终聚焦于区分当前吸毒行为并排除外部污染。尽管已有人提出利用毛发中的主要代谢物苯甲酰爱康宁（BE）的定量临界值来区分可能的当前吸毒行为与被动接触，但外源性形成的BE可能导致检测结果呈假阳性。因此，较少被检测到的COC代谢物去甲可卡因（NCOC）的存在，可能有助于提高对非法使用COC的确信度，并评估环境污染的可能性。本研究的目的是观察疑似吸毒者临床群体中NCOC的检测模式，并评估NCOC在区分COC的全身暴露与外部污染以及评估可卡因使用强度方面的可能作用。对2011年1月至2013年5月间从Motherisk实验室采集的毛发样本进行气相色谱 - 质谱分析，以检测COC、BE和NCOC的存在情况。计算了不同COC浓度范围内NCOC的阳性率（%），以及NCOC作为不同COC使用情况生物标志物的灵敏度、特异性、阳性预测值和阴性预测值。在COC浓度范围（ng/mg）0.13 - 0.4（高于检测限，低于定量限）、0.4 - 3、3 - 6、6 - 10、10 - 14、>14内，NCOC的阳性率（%）分别为0.26、4.15、29.63、55.85、80.37和94.02；各范围之间所有阳性比较的p<0.0001。这些结果被用于确定不同COC使用水平的COC临界浓度。NCOC在高于0.13 ng/mg检测限时的存在预示着COC浓度超过14.00 ng/mg，其灵敏度、特异性、阳性预测值（PPV）和阴性预测值（NPV）分别为94.
