BIOMARKER: Phosphatidylethanol as a sensitive and specific biomarker—comparison with gamma‐glutamyl transpeptidase, mean corpuscular volume and carbohydrate‐deficient transferrin

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Abstract
Phosphatidylethanol (PEth), a direct ethanol metabolite, is detectable in blood for more than 2 weeks after sustained ethanol intake. Our aim was to assess the usefulness of PEth [comparing sensitivity, specificity and the area under the curve (AUC)] as compared with carbohydrate-deficient transferrin (CDT), gamma-glutamyl transpeptidase (GGT) and mean corpuscular volume (MCV), calculating the results from sober patients against those from alcohol-dependent patients during withdrawal. Fifty-six alcohol-dependent patients (ICD-10 F 10.25) in detoxification, age 43 years, GGT 81 U/l, MCV 96.4 fl, %CDT 4.2, 1400 g ethanol intake in the last 7 days (median), were included in the study. Over the time of 1 year, 52 samples from 35 sober forensic psychiatric addicted in-patients [age 34 years, GGT 16 U/l, MCV 91 fl, CDT 0.5 (median)] in a closed ward were drawn and used for comparison . PEth was measured in heparinized whole blood with a high-performance liquid chromatography method. GGT, MCV and %CDT were measured using routine methods. A receiver operating characteristic curve analysis was carried out, with 'current drinking status' (sober/drinking) as the state variable and PEth, MCV, GGT and CDT as test variables. The resulting AUC was 0.974 (P < 0.0001, confidence interval 0.932-1.016) for PEth. At a cut-off of 0.36 micromol/l, the sensitivity was 94.5% and specificity 100%. The AUC for CDT, GGT and MCV were 0.931, 0.894 and 0.883, respectively. A significant Spearman's rank correlation was found between PEth and GGT (r = 0.739), CDT (r = 0.643), MVC (r = 0.639) and grams of ethanol consumed in the last 7 days (r = 0.802). Our data suggest that PEth has potential to be a sensitive and specific biomarker, having been found in previous studies to indicate longer lasting intake of higher amounts of alcohol.