Evaluation of a new immunoassay for urinary ethyl glucuronide testing

The minor ethanol metabolite ethyl glucuronide (EtG) is used as a sensitive and specific test for recent alcohol consumption with clinical and forensic applications. This study evaluated a new enzyme immunoassay (DRI-EtG EIA, Microgenics Corp.) for determination of the EtG concentration in urine samples.

Evaluation was done using the kit calibrators (range 0-5.0 mg/L) and controls, an external quality control sample, and 400 consecutive urines from the routine samples pool. The measuring range was extended by dilution of urine samples with saline. Comparison was made with an established liquid chromatographic-mass spectrometric (LC-MS) method.

The intra- and inter-assay imprecision of the DRI-EtG EIA in the range 0.4-2.5 mg/L was <2.2% (coefficient of variation, CV), and the limit of quantification was <0.1 mg/L. For the 400 urine samples, the EtG concentrations obtained using the DRI-EtG EIA (mean 24.2 mg/L, range 0-830) and LC-MS method (mean 22.4 mg/L, range 0-959) showed an overall good and statistically significant agreement (r2 = 0.931, P < 0.0001).

These results indicated a high level of accuracy and selectivity of the DRI-EtG EIA for quantification of urinary EtG. In the absence of a commonly accepted cut-off limit for urinary EtG, a threshold of 0.5 mg/L (2.2 mumol/L) is proposed, to obtain a high sensitivity but avoid positive results due to unintentional ethanol exposure.