Selective detection of phosphatidylethanol homologues in blood as biomarkers for alcohol consumption by LC-ESI-MS/MS

Brief history of the alcohol biomarkers CDT, EtG, EtS, 5-HTOL, and PEth

This article traces the historical development of various biomarkers of acute and/or chronic alcohol consumption. Much of the research in this domain of clinical and laboratory medicine arose from clinics and laboratories in Sweden, as exemplified by carbohydrate deficient transferrin (CDT) and phosphatidylethanol (PEth). Extensive studies of other alcohol biomarkers, such as ethyl glucuronide (EtG), ethyl sulfate (EtS), and 5-hydroxytryptophol (5-HTOL), also derive from Sweden. The most obvious test of recent drinking is identification of ethanol in a sample of the person's blood, breath, or urine. However, because of continuous metabolism in the liver, ethanol is eliminated from the blood at a rate of 0.15 g/L/h (range 0.1-0.3 g/L/h), so obtaining positive results is not always possible. The widow of detection is increased by analysis of ethanol's non-oxidative metabolites (EtG and EtS), which are more slowly eliminated from the bloodstream. Likewise, an elevated ratio of serotonin metabolites in urine (5-HTOL/5-HIAA) can help to disclose recent drinking after ethanol is no longer measurable in body fluids. A highly specific biomarker of hazardous drinking is CDT, a serum glycoprotein (transferrin), with a deficiency in its N-linked glycosylation. Another widely acclaimed biomarker is PEth, an abnormal phospholipid synthesized in cell membranes when people drink excessively, having a long elimination half-life (median ~6 days) during abstinence. Research on the subject of alcohol biomarkers has increased appreciably and is now an important area of drug testing and analysis.

Phosphatidylethanol (PEth) in Blood as a Marker of Unhealthy Alcohol Use: A Systematic Review with Novel Molecular Insights

The Alcohol Use Disorders Identification Test (AUDIT) and its short form, the AUDIT-C, the main clinical instruments used to identify unhealthy drinking behaviors, are influenced by memory bias and under-reporting. In recent years, phosphatidylethanol (PEth) in blood has emerged as a marker of unhealthy alcohol use. This systematic review aims to investigate the molecular characteristics of PEth and summarize the last ten years of published literature and its use compared to structured questionnaires. A systematic search was performed, adhering to PRISMA guidelines, through "MeSH" and "free-text" protocols in the databases PubMed, SCOPUS, and Web of Science. The inclusion criteria were as follows: PEth was used for detecting unhealthy alcohol consumption in the general population and quantified in blood through liquid chromatography coupled to mass spectrometry, with full texts in the English language. Quality assessment was performed using the JBI critical appraisal checklist. Twelve papers were included (0.79% of total retrieved records), comprising nine cross-sectional studies and three cohort studies. All studies stratified alcohol exposure and quantified PEth 16:0/18:1 through liquid chromatography coupled to mass spectrometry (LC-MS) in liquid blood or dried blood spots (DBS) with lower limits of quantitation (LLOQ) ranging from 1.7 ng/mL to 20 ng/mL. A correlation between blood PEth level and the amount of alcohol ingested in the previous two weeks was generally observed. PEth interpretative cut-offs varied greatly among the included records, ranging from 4.2 ng/mL to 250 ng/mL, with sensitivity and specificity in the ranges of 58-100% and 64-100%, respectively. Although the biomarker seems promising, further research elucidating the variability in PEth formation and degradation, as well as the molecular mechanisms behind that variability, are necessary.

Miniature mass spectrometer-based point-of-care assay for measuring phosphatidylethanol in blood

We demonstrate proof-of-concept for point-of-care assessment of long-term alcohol consumption by measuring phosphatidylethanol in blood/dried blood spots with nano-electrospray ionization and MS/MS using a miniature mass spectrometer. 'Abstinence', 'moderate', and 'chronic' consumption could be distinguished rapidly for both sample types, and quantitative performance was obtained with blood (LoQ-100 ng mL^-1).

Blood Phosphatidylethanol Concentrations Following Regular Exposure to an Alcohol-Based Mouthwash

Direct biomarkers of ethanol are used to monitor individuals who are required to abstain from ethanol consumption. In recent years, blood phosphatidylethanol (PEth) has gained acceptance in clinical and forensic contexts as an abstinence marker. Its elimination half-life of several days provides a window of detection of days to weeks. However, there is no research addressing the extent of PEth formation related to extraneous ethanol exposures. To assess the degree of ethanol absorption and subsequent formation of blood PEth related a common extraneous exposure, regular use of an ethanol-containing mouthwash, we recruited 16 participants to gargle with an alcohol-based mouthwash (21.6% ethanol) 4 times daily, for 12 consecutive days. Blood was analyzed for PEth 16:0/18:1 by liquid chromatography-tandem mass spectrometry. Our hypothesis that blood PEth concentrations would not equal or exceed 20 ng/mL was confirmed. Although the data suggest that regular use of mouthwash is unlikely to result in suprathreshold PEth concentrations, this work highlights the importance of considering extraneous ethanol exposures in clinical decision-making and in future research.

Analysis of six different homologues of phosphatidylethanol from dried blood spots using liquid chromatography-tandem mass spectrometry

Phosphatidylethanol (PEth) is a direct biomarker for alcohol consumption consisting of a fraction of different ethanol-modified, homologue phospholipids. The aim of this study was to validate an ultra-high-performance liquid chromatography-tandem mass spectrometry method to quantitate six different homologues of PEth (16:0/18:1, 16:0/18:2, 16:0/20:4, 18:0/18:1, 18:0/18:2, and 18:1/18:1) from dried blood spots (DBSs). DBSs were prepared volumetrically (20 μL of whole blood) and extracted with 1 mL of methanol (0.02 ng/μL internal standards). PEth homologues were separated on a BEH C18 column (2.1 × 150 mm, 1.7 μm) using methanol and ammonium acetate buffer (25 mM) in a 7 min isocratic run. Multiple reaction monitoring mode was used for the detection of PEth and the internal standards. Calibrators (10-1000 ng/mL) and quality controls (40, 400, and 700 ng/mL) were prepared from spiked whole blood; external control samples were obtained from proficiency testing schemes. After a comprehensive validation of the method, quantitative patterns of the different homologues were investigated in PEth positive samples (n = 57) from patients in a transplant setting. Satisfactory chromatographic separation, sensitive detection, and reliable quantification of the PEth homologues in DBSs can be achieved using the liquid chromatography-tandem mass spectrometry (LC/MS/MS) procedure. Validation results, including accuracy, linearity, recovery, matrix effects, and in-process stability, complied with international standards, and the analytical performance of the procedure was not affected by the hematocrit of the blood samples. Different quantitative patterns of the investigated PEth homologues were observed in authentic samples from liver transplant patients. This method will enable the study of the kinetics of six PEth homologues simultaneously and investigate the meaning of the homologues' distribution in individuals.

Should phosphatidylethanol be currently analysed using whole blood, dried blood spots or both?

Phosphatidylethanol (PEth) are phospholipids produced through non-oxidative ethanol metabolism. They accumulate in red blood cells and have been traditionally analysed in whole blood as potential biomarkers for moderate to long-term alcohol consumption. More recently, their analysis in dried blood spots has been gaining favour, namely, due to the ease in sampling, transport and storage conditions required. This paper aims at providing a short comparative review between analysing PEth in whole blood and dried blood spots and the potential pitfalls that researchers may face when setting up PEth testing for clinical use.

Determination of the formation rate of phosphatidylethanol by phospholipase D (PLD) in blood and test of two selective PLD inhibitors

Phosphatidylethanol (PEth) is an alcohol biomarker formed from phosphatidylcholine (PC) by the enzyme phospholipase D (PLD) in the presence of ethanol. A drinking study revealed individual differences in maximum PEth levels after drinking to a targeted blood alcohol concentration (BAC) of 0.1%. This seemed to be due to different PLD activities in the tested persons. Furthermore, post-sampling formation of PEth occurred in blood samples, still containing alcohol. Therefore, a standardized in vitro test for measuring individual PEth formation rates was developed. Two PLD inhibitors were tested for their potency to inhibit post-sampling PEth formation. PEth-negative blood samples were collected from a volunteer. Ethanol was added in different concentrations (0.01-0.3% BAC) directly after blood sampling. The specimens were incubated at 37 °C. Aliquots were taken at the start of the incubation, and every hour until 8 h after start of incubation, and one sample was taken on subsequent days over 1 week. PEth 16:0/18:1 and PEth 16:0/18:2 were determined by online SPE-LC-MS/MS. Furthermore, this test system was applied to blood samples of 12 volunteers. For the inhibition tests, fresh blood (spiked with 0.1% ethanol) was spiked with 30, 300, 3000, or 30,000 nM of either halopemide or 5-fluoro-2-indolyl-deschlorohalopemide (FIPI), and incubated at 37 °C. PEth concentrations were determined hourly over 5 h on the first day and once on day 2 and day 3. PEth formation was linear in the first 7 h of incubation and dependent on the alcohol concentration. The formation rates of PEth 16:0/18:1 were 0.002 μmol L^-1 h^-1 (0.01% BAC), 0.016 μmol L^-1 h^-1 (0.1% BAC), 0.025 μmol L^-1 h^-1 (0.2% BAC), and 0.029 μmol L^-1 h^-1 (0.3% BAC). For PEth 16:0/18:2, the formation rates were 0.002 μmol L^-1 h^-1 (0.01% BAC), 0.019 μmol L^-1 h^-1 (0.1% BAC), 0.025 μmol L^-1 h^-1 (0.2% BAC), and 0.030 μmol L^-1 h^-1 (0.3% BAC). Maximum concentrations reached 431 ng/mL (PEth 16:0/18:1) and 496 ng/mL (PEth 16:0/18:2) at 0.3% BAC after 3 days. Maximum velocity (v_max) was not reached under these conditions. PEth formation in blood of the 12 volunteers ranged between 0.011 and 0.025 μmol L^-1 h^-1 for PEth 16:0/18:1 and between 0.014 and 0.021 μmol L^-1 h^-1 for PEth 16:0/18:2. PEth formation in human blood was inhibited by halopemide in a concentration-dependent manner. However, a complete inhibition was not achieved by the applied maximum concentration of 30,000 nM. FIPI showed a better inhibition of PEth formation. A complete inhibition could be achieved by a concentration of 30,000 nM for the first 24 h (for PEth 16:0/18:1) and for 48 h (for PEth 16:0/18:2). Formation of PEth was found to be dependent on the BAC. As a consequence, it is essential to inhibit PLD activity after blood collection to avoid post-sampling formation of PEth in blood samples with a positive BAC. Inhibition of PEth formation was more effective using FIPI, compared to halopemide.

Stability of Ethyl Glucuronide, Ethyl Sulfate, Phosphatidylethanols and Fatty Acid Ethyl Esters in Postmortem Human Blood

The lack of systematic studies on the stability of ethanol's non-oxidative metabolites in postmortem specimens restricts their use in forensic cases. This study aimed to compare the stability of ethyl glucuronide (EtG), ethyl sulfate (EtS), phosphatidylethanols (PEths) and fatty acid ethyl esters (FAEEs) in postmortem human blood. Three groups were established based on the level and source of ethanol: the blank group, the ethanol-spiked group and the ethanol-positive group. Each group contained six blood samples from different corpses. The samples in each group were placed at 37, 25, 4 and -20°C. Every 24 h for 7 days, 50 μL was collected from each sample. The levels of EtG, EtS, PEths and FAEEs were determined by liquid chromatography-mass spectrometry, and their stability was evaluated. EtG was not detected in the blank group, but it was found in samples in the ethanol-spiked group placed at 37°C, and it was degraded in the ethanol-positive group at 37 and 25°C. EtS showed no change in any of the groups. PEths were not detected in the blank group, but formation was found in the ethanol-spiked group at all temperatures. In the ethanol-positive group, PEth levels fluctuated at 37°C, decreased at 25°C and increased at -20°C. FAEEs were generated in the blank group and in the ethanol-spiked group at all temperatures. In the ethanol-positive group, FAEEs were degraded at 37 and 25°C but were generated at 4 and -20°C. EtS is a reliable biomarker of ethanol consumption, and EtG could be used as a biomarker at low temperatures (4 and -20°C), but PEths and FAEEs are not appropriate biomarkers of ethanol consumption.

Differences in the Synthesis and Elimination of Phosphatidylethanol 16:0/18:1 and 16:0/18:2 After Acute Doses of Alcohol

BACKGROUND

The purpose of this study was to examine the synthesis and elimination of phosphatidylethanol (PEth) 16:0/18:1 and 16:0/18:2 following the consumption of alcohol among 56 light and heavy drinkers.

METHODS

A transdermal alcohol monitor was used to promote alcohol absence 7 days prior, and 14 days after, alcohol consumption in the laboratory. Participants consumed a 0.4 or 0.8 g/kg dose of alcohol in 15 minutes. Blood and breath samples were collected before, at various times up to 360 minutes postconsumption, and 2, 4, 7, 11, and 14 days after alcohol consumption. Initial rates of PEth synthesis, 360 minutes area under the PEth pharmacokinetic curves (AUCs), and elimination half-lives were determined.

RESULTS

(i) Nonzero PEth levels were observed before alcohol dosing for most participants, despite 7 days of alcohol use monitoring; (ii) 0.4 and 0.8 g/kg doses of alcohol produced proportional increases in PEth levels in all but 1 participant; (iii) the initial rate of synthesis of both PEth homologues did not differ between the 2 doses, but was greater for PEth 16:0/18:2 than PEth 16:0/18:1 at both doses; (iv) the mean AUC of both PEth homologues was higher at 0.8 g/kg than at 0.4 g/kg; (v) the mean AUC of 16:0/18:2 was greater than that of PEth 16:0/18:1 at both alcohol doses; (vi) the mean half-life of PEth 16:0/18:1 was longer than that of PEth 16:0/18:2 (7.8 ± 3.3 [SD] days and 6.4 ± 5.0 [SD] days, respectively); and (vii) there were no sex differences in PEth 16:0/18:1 or 16:0/18:2 pharmacokinetics.

CONCLUSIONS

The results of this study support the use of PEth 16:0/18:1 and 16:0/18:2 as biomarkers for alcohol consumption. Because of consistent pharmacokinetic differences, the levels of these 2 PEth homologues may provide more information regarding the quantity and recentness of alcohol consumption than either alone.

Evaluation of a novel method for the analysis of alcohol biomarkers: Ethyl glucuronide, ethyl sulfate and phosphatidylethanol

Currently available markers and methods to evaluate alcohol consumption are indirect and suboptimal, or rely on self-report, which have inherent problems. Direct metabolites of alcohol, phosphatidylethanol (PEth), ethyl sulfate (EtS), and ethyl glucuronide (EtG), are known to improve diagnostic accuracy. In this study, methods were established for the identification of PEth in erythrocytes and EtG and EtS in serum using ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The three biomarkers were tested and validated in volunteer teetotalers (n = 4) and drinkers (n = 10), and applied in patients (n = 8) hospitalized with alcohol-related problems. Linearity of each assay was demonstrated from 22.5 to 900 nM for EtG, 40-3175 nM for EtS, and 21-750 nM for PEth. The methods were highly selective, precise (<5% coefficient of variation), and had optimal accuracy (within 10% of the nominal value) for all three analytes. Recovery for all three compounds exceeded 90%. A preliminary investigation into the window of detection of these biomarkers after a single occasion of moderate alcohol consumption revealed that EtG and EtS could be detected and quantified over the short term (days) and PEth over the long term (weeks). All three biomarkers showed high sensitivity and specificity in distinguishing between abstinence and any alcohol use at the cut-off values of 22.5 nM for EtG, 40 nM for EtS, and 21 nM for PEth. We have established simultaneous assays for EtG, EtS, and PEth for routine clinical use in confirming abstinence and exposure, and detecting under-reporting of alcohol use, relevant in clinical and non-clinical settings.

Assessing phosphatidylethanol (PEth) levels reflecting different drinking habits in comparison to the alcohol use disorders identification test - C (AUDIT-C)

In addition to monitoring problematic or harmful alcohol consumption, drinking experiments indicated the potential of phosphatidylethanols (PEth) in abstinence monitoring. To date, no profound evaluation of thresholds for the differentiation of abstinence from moderate drinking and for detection of excessive consumption based on PEth homologues exists. Investigations with a large group of healthy volunteers (n=300) were performed to establish PEth reference values reflecting different drinking habits. Blood samples were analyzed for PEth 16:0/18:1 and 16:0/18:2 by online-SPE-LC-MS/MS method. Results were compared to AUDIT-C questionnaires, to the amounts of alcohol consumed during the two-weeks prior to blood sampling, and were statistically evaluated. PEth concentrations were significantly correlated with self-reported alcohol consumption (r>0.69) and with AUDIT-C scores (r>0.65). 4.0% of 300 volunteers reported abstinence (AUDIT-C score: 0), no PEth was detectable in their blood. PEth 16:0/18:1 concentrations below the limit of detection of 10.0ng/mL match with abstinence and light drinking habits (≤10g pure alcohol/day). However, some volunteers classified as "excessive alcohol consumers" had negative PEth results. In the group of volunteers classified as "moderate drinkers" (AUDIT-C score: 1-3 (women) and 1-4 (men)), 95% of the test persons had PEth 16:0/18:1 ranging from not detected to 112ng/mL, and PEth 16:0/18:2 ranging from not detected to 67.0ng/mL. Combination of self-reported alcohol consumption and AUDIT-C score showed that negative PEth results match with abstinence or light drinking. Moderate alcohol consumption resulted in PEth 16:0/18:1 from 0 to 112ng/mL and for PEth 16:0/18:2 ranged from 0 to 67.0ng/mL. Higher PEth concentrations indicated excessive alcohol consumption.

Identification and quantitation of phosphatidylethanols in oral fluid by liquid chromatography-tandem mass spectrometry

BACKGROUND

Phosphatidylethanols (PEth) are formed from phosphatidylcholines and ethanol and are used as a specific and sensitive alcohol biomarker. An analytical method for analysis of PEth in oral fluid based on high-performance liquid chromatography coupled to a quadrupole tandem mass spectrometer (LC-MS/MS) was developed and validated and applied on samples collected from patients undergoing alcohol detoxification.

METHODS

A 200-μL aliquot of oral fluid, collected using the QuantisalTM device, was extracted with chloroform/methanol containing internal standard and subjected to LC-MS/MS analysis of three selected PEth forms (16:0/16:0, 16:0/18:1, and 16:0/18:2). Chromatographic separation was achieved on a UPLC BEH phenyl column, using a mobile phase consisting of acetonitrile and water containing 10 mmol/L ammonium hydrogen carbonate with 0.1% ammonia. The MS instrument was operated in negative electrospray ionization and selected reaction monitoring mode.

RESULTS

The detection limit for PEth 16:0/16:0, 16:0/18:1, and 16:0/18:2 was ~0.1 ng/mL, and the extraction recoveries at 2.0 ng/mL were in the range of 99%-114%. Method linearity over a concentration range up to 200 ng/mL was ≥0.99. No significant deviation in results was observed in an analyte stability study of two different concentrations at two different temperatures over 3 months. In 35 oral fluid samples collected from patients undergoing alcohol detoxification, the highest concentration was observed for PEth 16:0/18:1 (Detected range, 0.51-55.3 ng/mL; mean, 8.5; median, 3.1). In addition, all three PEth forms were variably identified in a majority (63%) of the oral fluid samples. The PEth 16:0/18:1 values in oral fluid showed a weak positive correlation with the corresponding values in whole blood samples (r=0.50, p=0.026, n=20).

CONCLUSIONS

The LC-MS/MS method could reliably detect and quantify PEth in oral fluid samples collected after alcohol exposure. The method was characterized by validation data with satisfactory recovery, sensitivity, accuracy, and imprecision, and applied for analysis of clinical samples. The results suggest that measurement of PEth in oral fluid can be used as a biomarker for alcohol consumption, and as such a non-invasive complement to analysis in blood. However, further studies are required to evaluate the test characteristics (e.g. sensitivity and half-life) in comparison with PEth in blood.

Is it possible to detect PEth 16:0/18:1 and PEth 18:1/18:1 in red blood cells after 20 years of storage in liquid nitrogen?

INTRODUCTION

Phosphatidylethanol (PEth), as measured in freshly drawn blood samples, could be a promising new biomarker for habitual alcohol consumption, but it is still unknown whether PEth can also be determined from blood samples having been stored frozen for a longer period.

MATERIALS AND METHODS

PEth 16:0/18:1 and PEth 18:1/18:1 were determined by LC-MS/MS from red blood cells (RBC) derived from blood samples of (I) 20 healthy volunteers (after 1 month of storage at -80 °C) and (II) 232 participants of the population-based European Prospective Investigation into Cancer and Nutrition (EPIC)-Heidelberg study (after 20 years of storage at -196 °C). Analyses involved liquid-liquid extraction from 100 μl aliquots with phosphatidylpropanol (PProp 18:1/18:1) as the internal standard. Extracts were subjected to a 10-min LC gradient separation, using multiple reaction monitoring of deprotonated molecules for quantification.

RESULTS

After 1 month of storage at -80 °C, PEth was detectable in all samples at mean concentrations of 393.6 ± 12.4 ng/ml (PEth 16:0/18:1) and 43.3 ± 1.1 ng/ml (PEth 18:1/18:1). In samples stored for 20 years at -196 °C, PEth was detectable in 23.7% of all samples at mean concentrations of 412.2 ± 655.5 ng/ml (PEth 16:0/18:1) and 38.0 ± 74.8 ng/ml (PEth 18:1/18:1).

DISCUSSION AND CONCLUSION

PEth can be determined reliably from samples of moderate habitual alcohol consumers after 1 month of storage at -80 °C. Our data suggest that PEth is generally also detectable in samples after 20 years of storage at -196 °C. Further studies are needed to assess the still unknown impact of storage duration and temperature on different PEth specimen concentrations.

Phosphatidylethanol Detects Moderate-to-Heavy Alcohol Use in Liver Transplant Recipients

BACKGROUND

Alcohol-dependent liver transplantation (LT) patients who resume alcohol consumption are at risk for a number of alcohol-related problems including liver injury and liver failure. Post-LT patients are strongly advised to remain abstinent. However, we do not know how well this population complies due to a lack of valid methods (self-report and/or biomarkers) to identify alcohol use. Studies suggest as many as 50% resume alcohol use within 5 years. Phosphatidylethanol (PEth) is a new cell-membrane phospholipid biomarker to identify alcohol use in the past 28 days. This prospective study followed 213 LT recipients at 2 U.S. liver transplant centers.

METHODS

Sample included 213 LT subjects; 70.9% (n = 151/213) had a history of alcohol dependence prior to transplantation and 29.1% (n = 62/213) served as non-alcohol-dependent controls. Subjects participated in face-to-face interviews to assess alcohol use using a 30-day calendar. The protocol called for collecting blood samples at baseline, 6-, and 12-month follow-up.

RESULTS

Seventy percent (149/213) who reported no alcohol use had consistently negative PEth levels (<8 ng/ml). A total of 26.4% (57/213), 44 alcohol-dependent patients and 13 controls, had a positive PEth test of >8 ng/ml either at baseline and/or during the follow-up period. Alcohol-dependent subjects (23.8%; n = 36/151) and 16.1% (n = 10/62) controls reported no alcohol use but had at least 1 positive PEth test. Of the 11.2% (24/213) post-LT subjects who reported recent alcohol use, over half (11/24) had a positive PEth. The 13 self-reported alcohol users with a negative PEth level reported insufficient drinking to trigger PEth formation.

CONCLUSIONS

Adoption of PEth as part of routine posttransplant care of LT recipients will enable early identification of patients at risk of alcohol use and facilitate abstinence in patients with a history of alcohol dependence and alcohol-related liver damage.

Phosphatidylethanol in Postmortem Brain and Serum Ethanol at Time of Death

BACKGROUND

Phosphatidylethanol (PEth) is a metabolite of ethanol (EtOH), and its concentration in whole blood samples is a direct biomarker of alcohol consumption. Because PEth is also present in the brain and incorporated in lipid membranes, it can be used to classify deceased individuals on alcohol consumption status at the time of death. The purpose of this study was to detect PEth homologs in postmortem brains of individuals known to have had alcohol use disorder (AUD) and to determine the relationship between serum alcohol at the time of death and PEth in the cerebellum (CE) and orbital frontal cortex (OFC).

METHODS

Postmortem brain was collected and stored according to standard protocol. Psychiatric symptoms experienced prior to death were obtained by next of kin psychological autopsy to categorize subjects. Thirty male subjects were chosen for analyses: 10 with AUD with positive serum EtOH levels present at time of autopsy (AUD-W), 10 with AUD without positive serum EtOH levels (AUD-WO), and 10 controls. PEth 16:0/18:1 and 16:0/18:2 were quantified in 50 mg of CE and OFC of human postmortem brain using HPLC and mass spectrometric detection (triple quadrupole).

RESULTS

Results of this study were as follows: (i) PEth 16:0/18:1 and 16:0/18:2 were detected in the CE and OFC of all subjects diagnosed with AUD, (ii) PEth 16:0/18:1 levels were about 10-fold higher than PEth 16:0/18:2 in all subjects and both areas of brain, (iii) AUD-W subjects had higher PEth homolog levels in CE and OFC than controls and AUD-WO subjects, (iv) PEth 16:0/18:1, but not PEth 16:0/18:2, levels in CE and OFC of AUD-W subjects correlated significantly with serum EtOH levels at the time of death.

CONCLUSIONS

Quantification of combined PEth homolog levels in postmortem human brain is a good candidate as a diagnostic factor to classify drinking status, especially for those with AUD at the time of death. For alcohol research studies with postmortem brain, verification of drinking status is essential.

Associations Between the Phosphatidylethanol Alcohol Biomarker and Self-Reported Alcohol Use in a Sample of HIV-Infected Outpatient Drinkers in Western Kenya

BACKGROUND

To counteract the syndemics of HIV and alcohol in Sub-Saharan Africa, international collaborations have developed interventions to reduce alcohol consumption. Reliable and accurate methods are needed to estimate alcohol use outcomes. A direct alcohol biomarker called phosphatidylethanol (PEth) has been shown to validate heavy, daily drinking, but the literature indicates mixed results for moderate and nondaily drinkers, including among HIV-infected populations. This study examined the associations of the PEth biomarker with self-report alcohol use at 2 time points in 127 HIV-infected outpatient drinkers in western Kenya.

METHODS

Participants were consecutively enrolled in a randomized clinical trial to test the efficacy of a behavioral intervention to reduce alcohol use in Eldoret, Kenya. They endorsed current alcohol use, and a minimum score of 3 on the Alcohol Use Disorders Identification Test-Consumption or consuming ≥6 drinks per occasion at least monthly in the past year. Study interviews and blood draws were conducted at baseline and at 3 months post treatment from July 2012 through September 2013. Alcohol use was assessed using the Timeline Followback questionnaire. Blood samples were analyzed for the presence of the PEth biomarker and were compared to self-reported alcohol use. We also conducted semistructured interviews with 14 study completers in February through March 2014.

RESULTS

Baseline data indicated an average of moderate-heavy alcohol use: 50% drinking days and a median of 4.5 drinks per drinking day. At baseline, 46% of women (31 of 67) and 8% of men (5 of 60) tested negative for PEth (p < 0.001). At the 3-month follow-up, 93% of women (25 of 27) and 97% of men (30 of 31) who reported drinking tested positive, while 70% of women (28 of 40) and 35% of men (10 of 29) who denied drinking tested negative for PEth. Interviews were consistent with self-reported alcohol use among 13 individuals with negative baseline results.

CONCLUSIONS

These results add to the growing literature showing lack of agreement between self-report and PEth results among unhealthy and nondaily drinkers, particularly women. More research is needed to determine at what level of consumption over what period of time PEth becomes a reliable and accurate indicator of alcohol use.

Alternative sampling strategies for the assessment of alcohol intake of living persons

Monitoring of alcohol consumption by living persons takes place in various contexts, amongst which workplace drug testing, driving under the influence of alcohol, driving licence regranting programs, alcohol withdrawal treatment, diagnosis of acute intoxication or fetal alcohol ingestion. The matrices that are mostly used today include blood, breath and urine. The aim of this review is to present alternative sampling strategies that allow monitoring of the alcohol consumption in living subjects. Ethanol itself, indirect (carbohydrate deficient transferrin, CDT%) as well as direct biomarkers (ethyl glucuronide, EtG; ethyl sulphate, EtS; fatty acid ethyl esters, FAEEs and phosphatidylethanol species, PEths) of ethanol consumption will be considered. This review covers dried blood spots (CDT%, EtG/EtS, PEths), dried urine spots (EtG/EtS), sweat and skin surface lipids (ethanol, EtG, FAEEs), oral fluid (ethanol, EtG), exhaled breath (PEths), hair (EtG, FAEEs), nail (EtG), meconium (EtG/EtS, FAEEs), umbilical cord and placenta (EtG/EtS and PEth 16:0/18:1). Main results, issues and considerations specific to each matrix are reported. Details about sample preparation and analytical methods are not within the scope of this review.

Bioanalytical procedures and developments in the determination of alcohol biomarkers in biological specimens

Excessive alcohol consumption is a global problem, and consequently its evaluation is of great clinical and forensic interest. Alcohol biomarkers have been the focus of several research works in the past decades, with new compounds being studied in more recent years. The main objective of this review is to discuss topics for an analyst to consider when evaluating alcohol consumption through the analysis of alcohol biomarkers in biological specimens. For this, existing alcohol biomarkers will be reviewed, including carbohydrate-deficient transferrin, 5-hydroxytryptophol, ethanol, hemoglobin-associated acetaldehyde, fatty acid ethyl esters, ethyl glucuronide, ethyl sulfate and phosphatidylethanol. Additionally, their potential will be discussed, as well as analytical considerations, main challenges, limitations, data interpretation and existing methodologies for their determination in biological specimens.

Quantification of phosphatidylethanol 16:0/18:1, 18:1/18:1, and 16:0/16:0 in venous blood and venous and capillary dried blood spots from patients in alcohol withdrawal and control volunteers

Phosphatidylethanol species (PEths) are promising biomarkers of alcohol consumption. Here, we report on the set-up, validation, and application of a novel UHPLC-ESI-MS/MS method for the quantification of PEth 16:0/18:1, PEth 18:1/18:1, and PEth 16:0/16:0 in whole blood (30 μL) and in venous (V, 30 μL) or capillary (C, 3 punches (3 mm)) dried blood spots (DBS). The methods were linear from 10 (LLOQ) to 2000 ng/mL for PEth 16:0/18:1, from 10 (LLOQ) to 1940 ng/mL for PEth 18:1/18:1, and from 19 (LLOQ) to 3872 ng/mL for PEth 16:0/16:0. Extraction efficiencies were higher than 55% (RSD < 18%) and matrix effects compensated for by IS were between 77 and 125% (RSD < 10%). Accuracy, repeatability, and intermediate precision fulfilled acceptance criteria (bias and RSD below 13%). Validity of the procedure for determination of PEth 16:0/18:1 in blood was demonstrated by the successful participation in a proficiency test. The quantification of PEths in C-DBS was not significantly influenced by the hematocrit, punch localization, or spot volume. The stability of PEths in V-DBS stored at room temperature was demonstrated up to 6 months. The method was applied to authentic samples (whole blood, V-DBS, and C-DBS) from 50 inpatients in alcohol withdrawal and 50 control volunteers. Applying a cut-off value to detect inpatients at 221 ng/mL for PEth 16:0/18:1 provided no false positive results and a good sensitivity (86%). Comparison of quantitative results (Bland-Altman plot, Passing-Bablok regression, and Wilcoxon signed rank test) revealed that V-DBS and C-DBS were valid alternatives to venous blood for the detection of alcohol consumption.

Biomolecules and Biomarkers Used in Diagnosis of Alcohol Drinking and in Monitoring Therapeutic Interventions

BACKGROUND

The quantitative, measurable detection of drinking is important for the successful treatment of alcohol misuse in transplantation of patients with alcohol disorders, people living with human immunodeficiency virus that need to adhere to medication, and special occupational hazard offenders, many of whom continually deny drinking. Their initial misconduct usually leads to medical problems associated with drinking, impulsive social behavior, and drunk driving. The accurate identification of alcohol consumption via biochemical tests contributes significantly to the monitoring of drinking behavior.

METHODS

A systematic review of the current methods used to measure biomarkers of alcohol consumption was conducted using PubMed and Google Scholar databases (2010-2015). The names of the tests have been identified. The methods and publications that correlate between the social instruments and the biochemical tests were further investigated. There is a clear need for assays standardization to ensure the use of these biochemical tests as routine biomarkers.

FINDINGS

Alcohol ingestion can be measured using a breath test. Because alcohol is rapidly eliminated from the circulation, the time for detection by this analysis is in the range of hours. Alcohol consumption can alternatively be detected by direct measurement of ethanol concentration in blood or urine. Several markers have been proposed to extend the interval and sensitivities of detection, including ethyl glucuronide and ethyl sulfate in urine, phosphatidylethanol in blood, and ethyl glucuronide and fatty acid ethyl esters in hair, among others. Moreover, there is a need to correlate the indirect biomarker carbohydrate deficient transferrin, which reflects longer lasting consumption of higher amounts of alcohol, with serum γ-glutamyl transpeptidase, another long term indirect biomarker that is routinely used and standardized in laboratory medicine.

Phosphatidylethanol Compared with Other Blood Tests as a Biomarker of Moderate Alcohol Consumption in Healthy Volunteers: A Prospective Randomized Study

AIM

It is generally agreed that traditional alcohol biomarkers lack in sensitivity to detect hazardous alcohol consumption. The present study was undertaken to evaluate the ability of phosphatidylethanol (PEth) and traditional alcohol markers to detect moderate alcohol consumption and to distinguish between moderate alcohol consumption and abstinence.

METHODS

Forty-four subjects, 32 females and 12 males, were included in the study. They were randomized to alcohol abstention or to alcohol consumption. Female participants consumed 150 ml of red wine (equivalent to 16 g of alcohol) per 24 h and the male participants double the amount. The study lasted for 3 months. Blood samples were drawn at the start and at the end of the study period. Blood samples were analysed for PEth, carbohydrate-deficient transferrin (CDT), mean corpuscular volume (MCV), γ-glutamyltransferase (GGT), aspartate aminotransferase (AST) and alanine aminotransferase (ALT).

RESULTS

ROC curves for the various biochemical markers were plotted in order to assess their ability to discriminate between abstention and moderate daily consumption of alcohol. PEth and CDT were the only markers with AUROCs significantly higher than 0.5, and PEth was detected in all participants randomized to alcohol consumption.

CONCLUSION

PEth was the only marker that could detect moderate intake and the present results also indicate that PEth probably can distinguish moderate alcohol consumption from abstinence.

Progress in monitoring alcohol consumption and alcohol abuse by phosphatidylethanol

For early diagnosis and therapy of alcohol-related disorders, alcohol biomarkers are highly valuable. Concerning specificity, indirect markers can be influenced by nonethanol-related factors, whereas direct markers are only formed after ethanol consumption. Sensitivity of the direct markers depends on cut-offs of analytical methods, material for analysis and plays an important role for their utilization in different fields of application. Until recently, the biomarker phosphatidylethanol has been used to differentiate between social drinking and alcohol abuse. After method optimization, the detection limit could be lowered and phosphatidylethanol became sensitive enough to even detect the consumption of low amounts of alcohol. This perspective gives a summary of most common alcohol biomarkers and summarizes new developments for monitoring alcohol consumption habits.

Comparison of direct and indirect alcohol markers with PEth in blood and urine in alcohol dependent inpatients during detoxication

The importance of direct and indirect alcohol markers to evaluate alcohol consumption in clinical and forensic settings is increasingly recognized. While some markers are used to prove abstinence from ethanol, other markers are suitable for detection of alcohol misuse. Phosphatidyl ethanol (PEth) is ranked among the latter. There is only little information about the correlation between PEth and other currently used markers (ethyl glucuronide, ethyl sulfate, carbohydrate deficient transferrin, gamma-glutamyl transpeptidase, and methanol) and about their decline during detoxification. To get more information, 18 alcohol-dependent patients in withdrawal therapy were monitored for these parameters in blood and urine for up to 19 days. There was no correlation between the different markers. PEth showed a rapid decrease at the beginning of the intervention, a slow decline after the first few days, and could still be detected after 19 days of abstinence from ethanol.

Phosphatidylethanol in blood as a marker of chronic alcohol use: a systematic review and meta-analysis

The present paper aims at a systematic review of the current knowledge on phosphatidylethanol (PEth) in blood as a direct marker of chronic alcohol use and abuse. In March 2012, the search through “MeSH” and “free-text” protocols in the databases Medline/PubMed, SCOPUS, Web of Science, and Ovid/Embase, combining the terms phosphatidylethanol and alcohol, provided 444 records, 58 of which fulfilled the inclusion criteria and were used to summarize the current evidence on the formation, distribution and degradation of PEth in human blood: (1), the presence and distribution of different PEth molecular species (2), the most diffused analytical methods devoted to PEth identification and quantization (3), the clinical efficiency of total PEth quantification as a marker of chronic excessive drinking (4), and the potential utility of this marker for identifying binge drinking behaviors (5). Twelve papers were included in the meta-analysis and the mean (M) and 95% confidence interval (CI) of total PEth concentrations in social drinkers (DAI ≤ 60 g/die; M = 0.288 μM; CI 0.208–0.367 μM) and heavy drinkers (DAI > 60 g/die; M = 3.897 μM; CI 2.404–5.391 μM) were calculated. The present analysis demonstrates a good clinical efficiency of PEth for detecting chronic heavy drinking.

Phosphatidylethanol (PEth) as a biomarker of alcohol consumption in HIV-positive patients in sub-Saharan Africa

BACKGROUND

Alcohol is heavily consumed in sub-Saharan Africa and affects HIV transmission and treatment and is difficult to measure. Our goal was to examine the test characteristics of a direct metabolite of alcohol consumption, phosphatidylethanol (PEth).

METHODS

Persons infected with HIV were recruited from a large HIV clinic in southwestern Uganda. We conducted surveys and breath alcohol concentration (BRAC) testing at 21 daily home or drinking establishment visits, and blood was collected on day 21 (n = 77). PEth in whole blood was compared with prior 7-, 14-, and 21-day alcohol consumption.

RESULTS

(i) The receiver operator characteristic area under the curve (ROC-AUC) was highest for PEth versus any consumption over the prior 21 days (0.92; 95% confidence interval [CI]: 0.86 to 0.97). The sensitivity for any detectable PEth was 88.0% (95% CI: 76.0 to 95.6) and the specificity was 88.5% (95% CI: 69.8 to 97.6). (ii) The ROC-AUC of PEth versus any 21-day alcohol consumption did not vary with age, body mass index, CD4 cell count, hepatitis B virus infection, and antiretroviral therapy status, but was higher for men compared with women (p = 0.03). (iii) PEth measurements were correlated with several measures of alcohol consumption, including number of drinking days in the prior 21 days (Spearman r = 0.74, p < 0.001) and BRAC (r = 0.75, p < 0.001).

CONCLUSIONS

The data add support to the body of evidence for PEth as a useful marker of alcohol consumption with high ROC-AUC, sensitivity, and specificity. Future studies should further address the period and level of alcohol consumption for which PEth is detectable.

Formation of phosphatidylethanol and its subsequent elimination during an extensive drinking experiment over 5 days

BACKGROUND

For almost 30 years, phosphatidylethanol (PEth) has been known as a direct marker of alcohol consumption. This marker stands for consumption in high amounts and for a longer time period, but it has been also detected after 1 high single intake of ethanol (EtOH). The aim of this study was to obtain further information about the formation and elimination of PEth 16:0/18:1 by simulating extensive drinking.

METHODS

After 3 weeks of alcohol abstinence, 11 test persons drank an amount of EtOH leading to an estimated blood ethanol concentration of 1 g/kg on each of 5 successive days. After the drinking episode, they stayed abstinent for 16 days with regular blood sampling. PEth 16:0/18:1 analysis was performed using liquid chromatography-tandem mass spectrometry (high-performance liquid chromatography 1100 system and QTrap 2000 triple quadrupole linear ion trap mass spectrometer. Values of blood alcohol were obtained using a standardized method with headspace gas chromatography flame ionization detector.

RESULTS

Maximum measured concentrations of EtOH were 0.99 to 1.83 g/kg (mean 1.32 g/kg). These values were reached 1 to 3 hours after the start of drinking (mean 1.9 hours). For comparison, 10 of 11 volunteers had detectable PEth 16:0/18:1 values 1 hour after the start of drinking, ranging from 45 to 138 ng/ml PEth 16:0/18:1. Over the following days, concentrations of PEth 16:0/18:1 increased continuously and reached the maximum concentrations of 74 to 237 ng/ml between days 3 and 6.

CONCLUSIONS

This drinking experiment led to measurable PEth concentrations. However, PEth 16:0/18:1 concentrations stayed rather low compared with those of alcohol abusers from previous studies.

Quantitative profiling of phosphatidylethanol molecular species in human blood by liquid chromatography high resolution mass spectrometry

Phosphatidylethanol (PEth) is a group of aberrant phospholipids formed in cell membranes in the presence of ethanol by the catalytic action of the enzyme phospholipase D on phosphatidylcholine. Recently published literature has demonstrated the existence of several molecular species of PEth in samples drawn from alcohol-dependent subjects. A novel liquid chromatography high-resolution mass spectrometry (LC-HRMS) method coupled with a lipidomic strategy was developed and validated for the quantitative profiling of PEth molecular species in human blood collected from heavy and social drinkers. Chromatography was performed on a C18 column using acetonitrile, 10mM ammonium acetate, and 2-propanol as mobile phases with a 22-min gradient. HRMS experiments were performed on an LTQ-Orbitrap XL hybrid mass spectrometer equipped with an electrospray ionization source operated in negative ion mode. The theoretical masses of [M-H](-) of PEth species were calculated from the elemental chemical formula by varying the length and unsaturation grade of the fatty acid side chains; identification of PEth species in blood was achieved by searching the accurate masses of the targeted compounds in the acquired full-scan LC-HRMS chromatogram. The chemical structure of tentatively identified PEth species was elucidated through HR multiple mass experiments. The validated LC-HRMS method was selective, as warranted by HRMS at 60,000 resolution and 4 ppm accuracy. Linearity was observed in the 0.001-2.000 μM range, and limit of detection of 0.0005 μM and limit of quantitation of 0.001 μM were obtained for single PEth species. Imprecision and inaccuracy were always lower than 10% and 15%, respectively. The identification capabilities of the method were tested on blood samples collected from heavy drinkers (n=11), social drinkers (n=8), and teetotalers (n=10). The high sensitivity of the method led to the simultaneous identification of 17 different PEth molecular species in blood collected from heavy drinkers, and 2 PEth species (16:0/18:1 and 16:0/18:2) in blood collected from social drinkers.

LC-MS/MS analysis of phosphatidylethanol in dried blood spots versus conventional blood specimens

Phosphatidylethanol (PEth), which is formed extrahepatically by the action of phospholipase D on phosphatidylcholine in the presence of ethanol, has been suggested as a promising marker of alcohol misuse. Analysis of dried blood spots (DBS) is particularly advantageous for the determination of delicate analytes such as PEth. Therefore, measurement of PEth species (18:1/18:1, 16:0/18:1) in DBS versus whole blood was performed to ascertain whether respective results are directly comparable. Samples were obtained from subjects (n = 40) undergoing alcohol detoxification treatment. Analysis involved liquid-liquid extraction from both, DBS and whole blood (100 μL, respectively), with phosphatidylpropanol as the internal standard. Extracts were subjected to LC gradient separation using multiple reaction monitoring of deprotonated molecules. Results from measurements of corresponding DBS and whole blood specimens were compared by estimating the respective mean values and by a Bland and Altman analysis. Concentrations of PEth 18:1/18:1 ranged from 46.1 to 3,360 ng/mL in whole blood (mean, 461.7 ng/mL) and from 35.8 to 3,360 ng/mL in DBS (mean, 457.6 ng/mL); for PEth 16:0/18:1, concentrations were from 900 to 213,000 ng/mL (mean, 23,375 ng/mL) and 922-213,000 ng/mL (mean, 23,470 ng/mL) in blood and DBS, respectively. Estimated mean differences were -4.3 ng/mL for PEth 18:1/18:1 and 95.8 ng/mL for PEth 16:0/18:1. The Bland-Altman plot of both PEth species showed that the variation around the mean difference was similar all through the range of measured values and that all differences except one were within the limits of agreement. It could be shown that the determination of PEth species in DBS is as reliable as in whole blood samples. This assay may facilitate monitoring of alcohol misuse.

Phosphatidylethanol in blood (B-PEth): a marker for alcohol use and abuse

Phosphatidylethanol (PEth) represents a group of glycerophospholipid homologues where ethanol by phospholipase D has been bound at the position that normally contains an amino-alcohol. Since the formation of PEth is specifically dependent on ethanol, the diagnostic specificity of PEth as an alcohol biomarker is theoretically 100%. The half-life of PEth in blood is approximately 4 days. The amount of alcohol consumed correlates to blood concentration of PEth and PEth has been shown to be a more sensitive indicator of alcohol consumption than traditional alcohol markers, such as CDT (carbohydrate-deficient transferrin), GGT (γ-glutamyl transferase), and MCV (mean corpuscular volume) or a combination of these. Almost all clinical data so far available are based on a high performance liquid chromatography (HPLC) method with limited analytical sensitivity. With the advent of methods with considerably higher analytical sensitivity (e.g. mass spectrometric methods), clinical sensitivity will increase correspondingly. The possibility of determining very low concentrations of PEth by new sensitive analytical techniques may, however, have both ethical and legal consequences that have to be considered.

Alcohol biomarkers in applied settings: recent advances and future research opportunities

During the past decade, advances have been made in the identification, development, and application of alcohol biomarkers. This is important because of the unique functions that alcohol biomarkers can serve in various applied settings. To carry out these functions, biomarkers must display several features including validity, reliability, adequacy of temporal window of assessment, reasonable cost, and transportability. During the past two decades, several traditional alcohol biomarkers have been studied in multiple human studies. Meanwhile, several new, promising biomarkers, including various alcohol metabolites and alcohol biosensors, are being explored in human studies. In addition, researchers have explored using biomarkers in combination and using biomarkers in combination with self-reports, resulting in increased sensitivity with little sacrifice in specificity. Despite these advances, more research is needed to validate biomarkers, especially the new ones, in humans. Moreover, recent advances in high-throughput technologies for genomics, proteomics, and metabolomics offer unique opportunities to discover novel biomarkers, while additional research is needed to perfect newly developed alcohol sensors. Development of more accurate biomarkers will help practicing clinicians to more effectively screen and monitor individuals who suffer from alcohol use disorders.