“Yes, I tested positive for phosphatidylethanol, yet my experts confirm my result is compatible with abstinence.”
Katleen Van Uytfanghe1, Liesl Heughebaert1, Emmanuel Abatih2, Christophe P. Stove1
1Laboratory of Toxicology, Department of Bioanalysis, Faculty of Pharmaceutical Sciences, Ghent University, Ottergemsesteenweg 460, 9000 Ghent, Belgium
2Fostering Innovative Research Based on Evidence (FIRE), Ghent University, Krijgslaan 281, 9000 Ghent, Belgium
Phosphatidylethanol (PEth) has become an important direct biomarker for alcohol intake. PEth increases the sensitivity of uncovering alcohol consumption and monitoring abstinence. With a reported half-life of up to 7 – 8 days, and PEth values easily over 300 ng/mL in cases of chronic and excessive alcohol use, it can take weeks for PEth values to drop below the decision limit for monitoring abstinence (20 ng/mL). The question arises whether abstinence can be confirmed based on two consecutive PEth positive results.
In order to answer this question, results from a large scale PEth monitoring study were used. Over 500 participants who agreed to stay sober for one month took 3 finger prick samples via self-sampling at home using volumetric absorptive micro sampling devices (VAMS, Mitra®, Neoteryx). PEth 16:0/18:1 was quantified using a validated liquid chromatography – tandem mass spectrometry method. Based on these data a population-based algorithm capable of predicting abstinence with 95% probability was set up by fitting a linear mixed effect model to discern patterns in PEth elimination over time and accounting for intra- and inter-individual variability in PEth scores. The latter was further included in a 2-step decision tree, looking (i) whether or not PEth-values fall outside the prediction interval, and (ii) whether the slope between two PEth values is compatible with abstinence. Validation of this decision three was based on data of 74 people reporting to drink alcoholic beverages, alcohol free beverages or having eaten liquor-containing sweets. Allowing a cut-off of “4 units spread over 14 days”, the sensitivity and specificity of the decision tree was 89%. This is a realistic cut-off compared to other reports on detectability of a single dose intake of ethanol.
In conclusion, monitoring the decrease in PEth, while the latter is still positive, can underpin claims of abstinence upon short term monitoring.
The excessive use of ethanol-based hand sanitizer does not provide a reasonable explanation for a positive phosphatidylethanol result
Joseph Jones1, Gary Reisfield2, Scott Teitelbaum2
1United States Drug Testing Laboratories, Inc Des Plaines, IL USA
2University of Florida College of Medicine Gainesville, FL USA
Aim: Phosphatidylethanol (PEth) is a long-term direct ethanol biomarker used to verify abstinence in a number of settings including substance use disorder treatment, license renewal, and family court1,2. PEth has demonstrated adequate sensitivity and specificity over the past 2 decades however the literature is limited with prospective studies challenging unintentional ingestion scenarios as a reasonable explanation for a PEth positive result using the commonly accepted cutoff of 20 ng/mL3. The specific aim of this study was to recruit 15 volunteers and follow their PEth (16:0/18:1) levels over the course of two weeks while using an excessive amount of ethanol-based hand sanitizer. Urine specimens were collected for ethyl glucuronide (EtG) and ethyl sulfate (EtS) analysis to verify abstinence during the study period.
Methods: Fifteen (15) volunteers were recruited for the study. The volunteers were instructed to remain abstinent for 5 days prior to the study and throughout the 2-week study protocol. The volunteers provided a dried blood spot specimen for PEth analysis, a urine specimen for EtG, EtS, and creatinine analysis, and female volunteers submitted to a test for pregnancy. The volunteers were provided a sufficient supply of urine collection supplies for the study and Purell® Advanced Hand Sanitizer Refreshing Gel (70% ethanol). The volunteers collected urine specimens daily while applying the hand sanitizer 24-100 times per day as instructed. Midway and on the last day of the study, the volunteers provided additional dried blood spot specimens for PEth analysis. Specimens were sent to United States Drug Testing Laboratories (USDTL, Des Plaines, IL, USA) for analysis.
Results: At this time, the study is ongoing with 9 of the 15 participants having completed the study. Eight out of 9 volunteers produced low level positive EtG and/or EtS urine specimens, as expected. Ninety-four (94) urine specimens were tested for EtG and EtS. Of these, 5 specimens exceeded the EtG 100 ng/mL cutoff (5.3%, mean = 621.8) and if positive ranged from 242 ng/mL to 1442 ng/mL. There were 9 specimens that exceeded the EtS 25 ng/mL cutoff (9.6%, mean = 73.1 ng/mL) and if positive ranged from 29 ng/mL to 150 ng/mL. At this time, no participant in this study produced a positive PEth (cutoff = 20 ng/mL) dried blood spot specimen.
Conclusion: Excessive use of ethanol-based hand sanitizer does not present a reasonable explanation for a positive PEth result. This study is ongoing and more research is needed to investigate this and other possible scenarios where unintentional ingestion may provide a reasonable explanation for a PEth positive result.
References
1. Isaksson, A., Walther, L., Hansson, T., Anderson, A., Alling, C. (2011) Phosphatidylethanol in blood (B-PEth): A marker for alcohol use and abuse. Drug Testing and Analysis, 3, 195-200.
2. Skipper, G., Thon, N., DuPont, R., Baxter, L., Wurst, F. (2013) Phosphatidylethanol: The potential role in further evaluating low positive urinary ethyl glucuronide and ethyl sulfate results. Alcoholism: Clinical and Experimental Research. 37(9), 1582-1586.
3. Reisfield, G., Teitelbaum, S., Jones, J., Mason, D., Bleiweis, M., Lewis, B. (2020) Blood phosphatidylethanol concentrations following regular exposure to an alcohol-based mouthwash. Journal of Analytical Toxicology. E Pub Ahead.
Variation in the relative isomer abundance of synthetic and biologically derived phosphatidylethanols and its consequences for reliable quantification
Marc Luginbühl1, Reuben S. E. Young3, Frederike Stöth2, Wolfgang Weinmann2, Stephen J. Blanksby3, Stefan Gaugler1
1CAMAG, Sonnenmattstrasse 11, 4132 Muttenz, Switzerland
2Institute of Forensic Medicine Bern, University of Bern, Switzerland
3Central Analytical Research Facility, Institute for Future Environments, Queensland University of Technology, Brisbane, Australia
Phosphatidylethanol (PEth) in human blood samples is a marker for alcohol usage. Typically, PEth is detected by reversed-phase liquid chromatography coupled with negative ion tandem mass spectrometry, investigating the fatty acyl anions released from the precursor ion upon collision-induced dissociation (CID).
It has been established that in other classes of asymmetric glycerophospholipids the unimolecular fragmentation upon CID is biased depending on the relative position (known as sn-position) of each fatty acyl chain on the glycerol backbone. As such, the use of product ions in selected-reaction-monitoring (SRM) transitions could be prone to variability if more than one regioisomer is present in either the reference materials or the sample.
Here, we have investigated the regioisomeric purity of three reference materials supplied by different vendors, labelled as PEth 16:0/18:1. Using CID coupled with ozone induced dissociation, the regioisomeric purity (% 16:0 at sn-1) was determined to be 76%, 80% and 99%. The parallel investigation of the negative ion CID mass spectra of standards revealed differences in product ion ratios for both fatty acyl chain product ions and ketene neutral loss product ions.
Furthermore, investigation of the product ion abundances in CID spectra of PEth within authentic blood samples appears to indicate a limited natural variation in isomer populations between samples, with the cannonical, PEth 16:0/18:1 (16:0 at sn-1) predominant in all cases. Different reference material isomer distributions led to variation in fully automated quantification of PEth in 56 authentic dried blood spot (DBS) samples when a single quantifier ion was used.
Our results suggest caution in ensuring the regioisomeric composition of reference materials are well-matched with the authentic blood samples.
PEth – What we know and what we do not know about the alcohol biomarker
Frederike Stöth1, Wolfgang Weinmann1
1Institute of Forensic Medicine Bern, University of Bern, Bühlstrasse 20, 3012 Bern, Switzerland
Phosphatidylethanol (PEth) is a group of abnormal phospholipids. At least 48 analogues of phosphatidylethanols are known. The major and most often tested PEth is the analogue 16:0/18:1. The analogue 16:0/18:2 might play an important role for interpretation of findings, too. PEth is formed by the enzyme phospholipase D (PLD) from phosphatidylcholine in the presence of ethanol. Inter-individual differences in formation rates may lead to different PEth concentrations. Since it is only formed, as long as ethanol is present in the blood, also the individual elimination kinetics of ethanol plays an important role, even if the same amounts of ethanol are consumed per kg body weight. Various factors such as age and water content, weight/height – and tolerance, which might lead to faster elimination of ethanol, influence the kinetics of ethanol and thus PEth.
PEth is of great interest especially in withdrawal therapy and for abstinence monitoring. The elimination half-life of PEth is shorter at the beginning and longer in the terminal phase, ranging from 3 to up to 14 days. Biphasic elimination has been suggested from studies with patients in maintenance therapy. Therefore, and since PEth accumulates after repeated alcohol consumption, at least two PEth values should be analysed to confirm abstinence during withdrawal.
The patients in withdrawal clinics often start with PEth concentrations with a median of 1500 ng/mL which means that several weeks may be needed before they drop below suggested cut-off levels and a relapse may be detected by significant elevation of PEth concentrations.
Different cut off levels are discussed for abstinence. There is no agreement yet among different countries, but the value of 20 ng/ml is under discussion as cut-off for abstinence monitoring. However, not enough volunteer studies with low drinking amounts (below 0.5 g/kg ethanol concentration) are available, to define a cut-off for abstinence.
Comparison of the extraction of PEth homologues from human venous blood using isopropanol, isopropanol/hexane or methanol
Nathalie Hill-Kapturczak1, Brian H. Chen2, John D. Roache 1,3, Tara E. Karns-Wright1, Donald M. Dougherty1, Marisa Lopez-Cruzan1, Brett Ginsburg1, Wouter Koek1,3, Martin A. Javors1,3
1The University of Texas Health San Antonio – Department of Psychiatry, San Antonio, TX, 78229, USA.
2Life Epigenetics, Inc., Minneapolis, MN, 55402, USA,
3The University of Texas Health San Antonio – Department of Pharmacology, San Antonio, TX, 78229.
Objectives: The purpose of this study was to compare isopropanol alone (IPA), isopropanol plus hexane (IPA/Hex), and methanol alone (MeOH) for the extraction of phosphatidylethanol (PEth) 16:0/18:1, 16:0/18:2, and 16:0/20:4 from uncoagulated venous blood (VB) and dried blood spot (DBS) samples.
Methods: Participants were recruited from a retail space in downtown Minneapolis, MN, USA. Blood samples from 20 participants were collected by venipuncture in the arm. The VB were stored at 4°C for up to 24 hours and then at -80°C until the day of the PEth assay. Fifty microliters of VB were placed on spot cards and allowed to dry overnight. PEth homologues were extracted from VB and DBS using IPA, IPA/Hex or MeOH using aliquots of the same blood samples. PEth homologue levels were quantified using HPLC/MS/MS.
Results: For PEth extracted from VB with IPA/Hex (x-axis) vs. IPA (y-axis), the Spearman r values were ≥ 0.97, and the slopes were 1.73, 2.27, and 1.48 for PEth 16:0/18:1, 16:0/18:2, and 16:0/20:4 levels, respectively. For VB extracted with MeOH (x-axis) vs. IPA (y-axis), the Spearman r values were ≥ 0.97, and the slopes were 0.94, 1.03, and 1.23, for PEth 16:0/18:1, 16:0/18:2, and 16:0/20:4, respectively. For PEth 16:0/18:1, 16:0/18:2, and 16:0/20:4 levels from VB extracted with IPA/Hex (x-axis) vs. MeOH (y-axis), the Spearman r values were ≥ 0.99, and the slopes were 1.80, 1.70, and 0.782, respectively. For DBS extracted with IPA (x-axis) vs. IPA/Hex (y-axis), the Spearman r values were ≥ 0.93, and the slopes were 1.12, 1.02, and 0.977 for PEth 16:0/18:1, 16:0/18:2, and 16:0/20:4 levels, respectively. For 16:0/18:1, 16:0/18:2, and 16:0/20:4 in DBS extracted with MeOH (x-axis) vs. IPA (y-axis), the Spearman r values were ≥ 0.96, and the slopes were 1.59, 1.60, and 1.47, respectively. The Spearman r values were ≥ 0.94, and the slopes were 1.93, 1.73, and 1.46 for PEth 16:0/18:1, 16:0/18:2, and 16:0/20:4 levels, respectively, for DBS extracted with MeOH (x-axis) vs. IPA/Hex (y-axis).
Conclusion: In VB, IPA and MeOH resulted in higher PEth levels than IPA/Hex. However, in DBS, IPA and IPA/Hex resulted in higher PEth levels than MeOH.
Phosphatidylethanol for monitoring alcohol use in liver transplant candidates: an observational study
Pablo Barrio1*, Antoni Gual1, Anna Lligoña1 , Lidia Teixidor1, Wolfgang Weinmann2, Michel Yegles3 and Friedrich M. Wurst4
1Grup Recerca Addicions Clínic (GRAC-GRE), Department of Psychiatry, Clinical Institute of Neuroscience, Hospital Clínic i Universitari de Barcelona, Universitat de Barcelona, IDIBAPS, RTA (RETICS), Villarroel, 170, 08036 Barcelona, Spain; tgual@clinic.cat (A.G.); alligona@clinic.cat (A.L.); lteixido@clinic.cat (L.T.)
2Institute of Forensic Medicine, University of Bern, 3012 Bern, Switzerland; Wolfgang.Weinmann@irm.unibe.ch
3Laboratoire National de Santé, Service de Toxicologie, 3555 Dudelange, Luxembourg; michel.yegles@lns.etat.lu
4Psychiatric University Hospital, 4002 Basel, Switzerland; frieder.wurst@gmx.de
Liver transplantation remains an essential procedure for many patients suffering from alcoholic liver disease. Alcohol use monitoring remains paramount all through the stages of this complex process. Direct alcohol biomarkers, with improved specificity and sensitivity, should replace traditional indirect markers. Phosphatidylethanol (PEth) has been recently tested in alcoholic liver disease patients, but more evidence is needed, especially in comparison with other direct biomarkers. We conducted an observational study among patients awaiting liver transplantation. We analyzed PEth in blood, ethyl glucuronide (EtG) in hair and urine and ethyl sulphate (EtS) in urine, using mass spectrometry methods. In addition, transaminases, and self-reports were analyzed. A total of 50 patients were included (84% men, mean age 59 years (SD = 6)). 18 patients (36%) screened positive for any marker. Self-reports were positive in 3 patients. EtS was the biomarker with more positive screens. It also was the most frequently exclusive biomarker, screening positive in 7 patients who were negative for all other biomarkers. PEth was positive in 5 patients, being the only positive biomarker in 2 patients. It showed a false negative in a patient admitting alcohol use the previous week and screening positive for EtG and EtS. Hair EtG was positive in 3 patients who had negative PEth, EtG. EtG did not provide any exclusive positive result. A combination of biomarkers seems to be the best option to fully ascertain abstinence in this population. Our study suggest EtS might also play a significant role.
Phosphatidylethanol (PEth) alcohol biomarker sensitivity among adults reporting unhealthy alcohol use: An individual patient data meta-analysis
Judith A. Hahn1, Pamela Murnane, Eric Vittinghoff, Kendall Bryant, Winnie R. Muyindike, Nneka I. Emenyonu, Robin Fatch, Gabriel Chamie, Jessica Haberer, Joel Francis, Karen Jacobson, Bronwyn Myers, Marie Claude Couture, Kimberly Page, Ralph DiClemente, Jennifer Brown, Kaku So Armeh, Jeffrey Samet, Richard Saitz, Mark Sulkowski, Gregory Marcus, Sarah Woolf-King, Robert L. Cook, Veronica Richards, Patricia Molina, Tekeda Ferguson, David Welsch, Mariann R. Piano, Shane Phillips, Scott Stewart, Majid Afshar, Amy Justice, David Fiellin, Kathleen McGinnis
1Division of HIV, ID, and Global Medicine, Department of Medicine, University of California, San Francisco
Aims: Objective measurement or alcohol consumption is important for clinical care and research. We aimed to examine factors associated with the detection of phosphatidylethanol (PEth), an alcohol metabolite, among people reporting alcohol use at a level for which PEth is expected to be positive.
Design: Individual participant data meta-analysis.
Participants: We identified 21 studies on 4 continents, and included 4073 observations from 3085 participants with unhealthy alcohol use, based on the Alcohol Use Disorders Identification Test – Consumption (AUDIT-C) or measures available to calculate the AUDIT-C, and with PEth testing results (homologue 16:0/18:1, limit of quantification 8 ng/mL) available.
Measurements: We fit mixed effects models with random intercepts for study site to examine the associations between demographics (biologic sex, race/ethnicity, and age), biologic variables (body mass index [BMI], hemoglobin, HIV status, and liver fibrosis [Fib-4], and method of blood collection (venous versus finger-prick) and PEth positivity (≥8 ng/mL), adjusting for AUDIT-C score. We also explored effect modification by biological sex and race/ethnicity, and conducted stratified and sensitivity analyses
Findings: One-third (31%) of participants were women, median age was 38 (range: 17-89); 32% were African, 28% African American, 28% White, and 12% other race/ethnicity. Seventy-nine percent (79%) were PEth positive. After adjusting for AUDIT-C score, we found no associations of sex, race/ethnicity, age, or method of blood collection with PEth positivity in multivariable analyses. However, we did find associations with biologic variables; higher hemoglobin and indeterminate and advanced fibrosis were associated with higher odds of PEth positivity, while higher BMI and HIV infection were associated with lower odds of PEth positivity. We found significant interactions by race/ethnicity, and in stratified analyses, the odds of PEth positivity were significantly lower for women versus men among African Americans.
Conclusions: Adjusting for self-reported alcohol use, biological factors such as hemoglobin, BMI, liver fibrosis, and HIV status were associated with PEth positivity among people reporting unhealthy alcohol use, while demographic factors and method of blood collection showed no association. Further research is needed to understand how to factor in patient characteristics when interpreting PEth testing results.
Fully automated correction for the hematocrit bias of non-volumetric dried blood spot phosphatidylethanol analysis
Stefan Gaugler1, Frederike Stöth2, Wolfgang Weinmann2, Marc Luginbühl1
1CAMAG DBS Laboratory, Sonnenmattstrasse 11, 4132 Muttenz, Switzerland
2Institute of Forensic Medicine Bern, University of Bern, Bühlstrasse 20, 3012 Bern, Switzerland
The quantitative analysis of substances in dried blood spots (DBS) has gained vast popularity in the past decade. The World Anti-Doping Agency (WADA) also recently committed to implementing DBS. Currently, DBS sampling mainly focused on various volumetric sampling devices such as Hemaxis, Capitainer, and Mitra. These devices are designed to collect a specific sample volume, independent of any hematocrit (HCT) effect to enable quantitative DBS analysis.
Here, we present an automated solution that makes the necessity of volumetric sampling for quantitative DBS analysis obsolete. Combining automated reflectance-based HCT correction in combination with fully automated DBS LC-MS/MS analysis, the novel strategy permits high-throughput analysis in combination with HCT independence. Studying the model compound Phosphatidylethanol 16:0/18:1, which is heavily HCT dependent, an implementation of DBS HCT results is presented: First, the performance of the automated HCT module with DBS is demonstrated compared to standardized HCT analysis from whole blood using a centrifuge. Second, the HCT dependency of fully automated PEth analysis from DBS is evaluated. Third, a solution to correct for the HCT dependency of PEth using the HCT scanner is presented.
The study demonstrates that as soon as the HCT dependence of the analyte is known, a correction factor can be applied for the normalization of HCT levels. In the context of PEth, a linear increase in PEth concentration was observed, as the analyte is primarily located within the cellular fraction. Based on the obtained results, the use of a common correction factor for PEth DBS is possible.
Stability of PEth in routine samples from three different blood collection approaches
C. Bartlitz, J. Neumann, Michael Böttcher
MVZ Medizinische Labore Dessau Kassel GmbH, Abteilung Drogen- und Medikamentenanalytik, Bauhüttenstrasse 6, 06847 Dessau-Roßlau, Germany
We investigated the stability of PEth (16:0/18:1) in random non-paired routine samples (PEth > 0.014 (LoQ) to 6.02 µmol/L) from three different blood collection approaches: intra-venous EDTA-whole blood (EWB), ethanol negative (<0.10 g/L, n=446) and positive samples (>0.10 g/L, n=83); capillary wet blood drop (CWBD, Sarstedt Minivette, n=542); capillary dried blood spot (DBS, Capitainer, n=368).
PEth analysis was performed on the day of sample arrival (d0) and after 28 days (d28) with our EN 17025/15189 accredited LC-MS/MS method. Whole blood quality control samples level 1 and 2 from ACQ Science and self-prepared level 3 (target: 0.057 µmol/L, n= 28; 0.452 µmol/L, n=40; 2.845 µmol/L, n=104) so far revealed biases from -7.1% to 6.6% with CVs from 5.1% to 9.6%. Samples were stored at 4°C (EWB, CWBD) or at room temperature (DBS). The PEth recovery was expressed by the d28/d0 concentration ratio.
For EWB and DBS the mean and median ratios were similar but the CV differed widely. No difference between ethanol-negative and ethanol-positive EWB samples was observed. Interestingly, a higher mean and median was found for CWBD samples. The large number of outliers with a strong tendency towards increased PEth values after 28 days was somewhat surprising, especially for the CWBD and DBS group. QC data showed that this could not be explained by the measurement uncertainty alone. In addition, post-collection PEth formation in the presence of ethanol seemed to be unlikely and was excluded for the EWB group.
Sensitivity and specificity of PEth as predictor of drinking observed in the past two weeks
John D. Roache1,2, Tara E. Karns-Wright1, Wouter Koek1,2,3, Martin A. Javors1,2, Donald M. Dougherty1, Marisa Lopez-Crusan1, Brett Ginsburg1, and Nathalie Hill-Kapturczak1
1University of Texas Health at San Antonio – Department of Psychiatry & Behavioral Sciences
2University of Texas Health at San Antonio – Department of Pharmacology
3University of Texas Health at San Antonio Department of Cell Systems & Anatomy
Objectives: Phosphatidylethanol (PEth) is increasingly used to objectively detect drinking in a criminal, civil, employment and other proceedings. We sought to empirically establish ng/ml cut-off values of Phosphatidylethanol (PEth) that may be useful to detect drinking alcohol levels of any drinking, or various definitions of heavy or harmful drinking among research volunteers freely drinking as usual while completing self-reports of drinking daily.
Methods: Each day for 28 days, participants completed online reports of drinking the day before to monitor patterns of naturalistic drinking in n=14 males and n=15 females. Participants also came in once weekly to provide blood samples for the measurement of PEth levels. Regression analysis evaluated the relationships between observed ng/ml levels of PEth each week and levels of any drinking, or various definitions of heavy or harmful drinking over varying periods of time. Sensitivity and Specificity analysis were used to evaluate previously proposed cut-offs of 20 ng/ml to detect “significant” drinking, and 200 ng/ml to detect sustained heavy drinking, and to determine an experimentally observed cut-off that optimizes signal detection.
Results: Over the four weeks of study, week to week drinking was fairly stable, as were also PEth levels. Males reported more drinks per drinking day and more frequent days of heavy drinking than females. A number of analyses consistently showed between subject positive correlations of drinking levels and observed PEth levels and there were no sex differences in this relationship. Regression analyses demonstrated that periods of approximately 10 days of drinking were the optimum time period to predict observed PEth levels or PEth level increases in repeated sampling. Use of the 20 ng/ml threshold for detection had good sensitivity but poor specificity for detection of drinking regardless of the type of drinking (i.e., “any”, “problematic”, or “heavy”) observed over 1 or 2 weeks before PEth measurement. Conversely, the 200 ng/ml cut-off had good specificity, but poor sensitivity. Empirically-derived cut-offs in the 29-36 ng/ml range exhibited the best signal detection characteristics, achieving 87% sensitivity and 100% specificity for one or more days of heavy drinking in the past two weeks.
Conclusion: We have confirmed consistent relationships between observed PEth levels and drinking over the previous 1-2 weeks. We also showed that 10 days of drinking was the optimal time-period for assessment of drinking and there were no sex differences in the PEth-drinking relationship. As a biomarker of recent alcohol consumption, signal-dection characteristics were optimized for the detection of any “heavy” drinking but only when using PEth threshold cut-offs in the 29-36 ng/ml range. We suggest the need to increase the commonly used threshold value of 20 ng/ml to protect against specificity errors.
The ratio of phosphatidylethanol (PEth) 16:0/18:1 to PEth 16:0/18:2 as an indicator of recent abstinence from alcohol consumption
Martin A. Javors, Nathalie Hill-Kapturczak, John D. Roache, Tara E. Karns-Wright, Marisa Lopez-Cruzan, Brett Ginsburg, and Donald M. Dougherty
Department of Psychiatry and Behavioral Health, UT Health-Long School of Medicine, San Antonio, Texas 78229
PEth 16:0/18:1 and 16:0/18:2 are metabolites of ethanol found in human red blood cells. Their measurement in whole blood samples is used as a direct biomarker for recent alcohol consumption during the previous 2 to 3 weeks. Previous studies have shown that the mean half-life of elimination of PEth 16:0/18:1 is longer than PEth 16:0/18:2, that is, whole blood PEth 16:0/18:1 concentration decreases more slowly than PEth 16:0/18:2. The calculated ratio of the concentrations of PEth 16:0/18:1 divided by that of 16:0/18:2 increases during abstinence. The purpose of this study was to characterize the pharmacokinetics of the “ratio” and determine its value as an indicator of recent abstinence.
Methods. Fasted male and female participants (N=53) received either 0.4 or 0.8 g/kg oral ethanol doses during a 15 min period after a 7 day period of alcohol abstinence. Blood samples were collected before and during the 6 hour period after the ethanol dose and then every 2 or 3 days during the next 14 days. PEth 16:0/18:1 and PEth 16:0/18:2 levels were quantified in uncoagulated whole blood samples by HPLC/MS/MS and the “ratio” of the concentrations was calculated at time points at which PEth homolog levels were detectable. Transdermal ethanol concentrations (TAC) were collected to identify drinking during the 14 day period after ethanol consumption. Break through drinking did occur.
Results. (1) the rate of PEth 16:0/18:1 synthesis was lower than that of PEth 16:0/18:2 during 6 h after 0.4 g/kg and 0.8 g/kg oral ethanol doses); (2) the rate of elimination (half-life) of PEth 16:0/18:1 was slower than that of PEth 16:0/18:2 during the 2 week abstinent period; (3) the mean “ratio” decreased immediately during the 6 hour period after in-lab alcohol consumption to 0.876 ± 0.53; (4) the mean “ratio” increased steadily in every participant to a mean of 2.04 ± 2.5 by the end of the 2 week abstinent period.
Conclusions. The observed systematic increases in the “ratio” appear to be more sensitive than either PEth homolog alone as an indicator of abstinence (funded by NIAAA RO1 AA022361 and the Karren Endowment in Psychiatry).