Urinary ethyl glucuronide for the assessment of alcohol consumption during pregnancy: comparison between biochemical data and screening questionnaires

Background: Ethyl glucuronide (EtG) is a metabolite of ethanol used as a marker of alcohol drinking and is identified in urine. Gestational alcohol drinking harms the fetus, so, disclosing any form of use and abuse of this substance during pregnancy is crucial. Many discovery methods have been planned to overcome this question, including that of using screening questionnaires as the AUDIT-C, T-ACE/TACER-3, and TWEAK. Aim: The aim and novelties of this study were to compare biochemical data from urinary EtG assays (cut-off 100 ng/mL for risking drinking behavior) with the outcome of questionnaires and of a food diary routinely used in our hospital; moreover, for the first time, we analyzed in pregnant women the EtG values normalized by the amount of creatinine excreted according to methods previously established [1]. Methods: Random urine samples were collected from 309 pregnant women immediately after being interviewed. EtG was quantified using an enzyme immunoassay and urinary creatinine was assessed using an enzymatic colorimetric method. Women that had not exhaustively answered one of the questionnaires, or that refused to provide urine samples were excluded. In the end, 309 women had a complete set of data and were considered for this study. Urine creatinine measurements were performed to determine if urine dilution might have resulted in false negatives in the challenge study. In order to accomplish this objective, as urinary creatinine concentrations are, on average, approximately 1 mg/mL, we used a normalized value of 100 ng EtG/mg Creatinine [1]. Results: Our data show that 20.4% of the pregnant women in the study were over the established normalized cut-off value. Poor to null concordance (unweighted k < 0.2) was found between EtG data and the screening interviews, that show, on average, lower levels of alcohol consumption. Conclusion: In conclusion, this study provides evidence that the assessment of maternal alcohol consumption during pregnancy, only indirectly estimated with questionnaires and food diary, can produce misleading ratings.