False-positive ethyl glucuronide immunoassay screening associated with chloral hydrate medication as confirmed by LC–MS/MS and self-medication

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• 作者：Torsten Arndt ; Birgit Gierten ; Brunhilde Gü ; ssregen ; Annika Werle ; Joachim Grü ; ner
• 关键词：Alcohol ; Chloral hydrate ; Ethyl glucuronide ; False-positive ; Enzyme immunoassay ; LC– ; MS
• 刊名：Forensic Science International
• 出版年：2009
• 出版时间：30 January 2009
• 年：2009
• 卷：184
• 期：1-3
• 页码：e27-e29
• 全文大小：159 K

文摘

Background

Urine-ethyl glucuronide (EtG) concentrations are considered as a specific marker of recent alcohol consumption. We describe false-positive EtG screening results by the DRI^® ethyl glucuronide enzyme immunoassay caused by chloral hydrate intake.

Methods

Urine-EtG-screening: DRI^® EtG enzyme immunoassay (Thermo Fisher Scientific Microgenics) on a Hitachi 912 analyzer. EtG- and ethyl sulfate (EtS) confirmatory analysis: LC–MS/MS with an ESI source in the negative ionization, selective reaction monitoring mode. Patient: ethanol-abstaining women under buprenorphine-treatment (medication with levetiracetam, gabapentin, clomethiazol and chloral hydrate). Proband: self-medication with 500 mg chloral hydrate after a 5-day ethanol abstinence. EtG analysis for both in subsequent urines. Check for cross reactions of the pharmaceuticals with the EtG immunoassay by addition of pure substance (2 g/L each) to EtG-free urine.

Results

EtG concentrations up to 8.0 mg/L or 7.0 mg/g creatinine (cut-off 0.5 mg/L or mg/g) for the patient and up to 0.28 mg/L or 0.35 mg/g for the control subject (after 500 mg chloral hydrate) were obtained by the immunoassay. LC–MS/MS could not confirm these EtG results. In fact, EtG and/or EtS were not detectable in any of the urine samples by LC–MS/MS (lower limit of detection 0.01 mg/L). Cross reactions of the pharmaceuticals, incl. the chloral hydrate metabolites trichloroethanol and trichloroacetic acid, with the DRI^® EtG immunoassay results were ruled out (by spiking experiments) as the underlying cause for the false-positive EtG immunoassay results.

Conclusions

Trichloroethyl glucuronide as an important chloral hydrate metabolite remains the most probable cross reacting substance with the DRI^® EtG immunoassay (unproven because of lack in pure standard). The chloral hydrate self-medication experiment clearly points to an association of the false-positive EtG immunoassay results and chloral hydrate intake. Chloral hydrate medication has to be considered as a cause for false-positive EtG screening results by the DRI^® EtG immunoassay even in cases with regular chloral hydrate treatment (250–1000 mg) and the more in patients with chloral hydrate tolerance (taking g/day). It is recommended that positive EtG immunoassay results always be confirmed by a more specific technique such as LC–MS/MS, including ethyl sulfate as a second minor ethanol metabolite.