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the microsampling blog

comparing PEth and liver function enzymes to monitor alcohol abuse

An article by Nouredine Sadeg et al at the International Medical Institute of Toxicology and two other institutions in France was published in the November 2023 edition of World Journal of Biological and Pharmaceutical Research. Their article describes the use of Mitra® microsampling devices based on VAMS® technology in a study comparing phosphatidylethanol, or PEth (a direct alcohol use biomarker), and indirect alcohol biomarkers in blood samples collected by study volunteers. The paper is entitled, “Phosphatidylethanol (PEth) in practice: A specific and proportional marker of alcohol consumption.”

monitor alcohol abuse The study, which is summarized here, showed that PEth was a far more reliable marker of alcohol consumption, which led the research group to conclude that measurement of PEth can be carried out using remote microsampling as part of a remote consultation, at a distance from the analytical labs or facilities.

The Importance of PEth to Monitor Alcohol Problems

In 2018, the World Health Organization (WHO) reported that alcohol abuse accounted for more than 5% of disease burden. Indeed, the paper by Nouredine Sadeg reports that in France 1.5 million people are reported to be alcohol dependent, with a further 2.5 million reported to engage in risky drinking. Statistics show that up to 49,000 deaths per year are attributed to alcohol abuse in France alone.

As discussed in a previous technical blog, there are a number of markers that can be employed to monitor alcohol abuse. These include direct biomarkers, such as ethylglucuronide (EtG), ethyl sulfate (EtS), acetaldehyde, acetic acid, fatty acid ethyl esters (FAEE), carbohydrate deficient transferrin (CDT) and, of course, palmitoyl-2-oleoyl-glycero-3-phosphoethanol (PEth 16:0/18:1). Out of these markers, PEth has recently been proven as the preferred direct marker due to its long half-life (4-5 days) and high clinical sensitivity and specificity.

Liver Function Enzyme Activity as Another Approach to Alcohol Monitoring

Another popular way to monitor alcohol abuse is to measure the indirect effects of the drug. There are two approaches to this. The first is to measure mean corpuscular volume of red blood cells (elevated in chronic drinkers). The second way is to measure serum liver enzyme activity.

When the liver is damaged, enzymes such as aspartate aminotransferase (AST), alanine aminotransferase (ALT), and gamma-glutamyl transferase (GGT) are released into the blood stream from damaged hepatocytes. Because excess alcohol consumption is a cause of liver damage, measurement of these indirect markers can be useful in measuring the ‘liver function’ in chronic alcohol abusers.

However, serum liver enzymes activity levels are not just specific to alcohol abuse but are indicative of general liver damage, from causes such as the hepatotoxic side effects of drugs or if the patient suffers from hepatitis. This makes use of liver enzyme activity measurement challenging with alcohol abuse patients if they are also taking medicine with hepatotoxic side effects or if they have viral hepatitis.

Comparing the Efficacy of Two Alcohol Monitoring Methods

finger-stick microsampling with MitraTo compare the efficacy of measuring PEth levels versus liver enzyme activity, Nouredine Sadeg et al recruited 57 volunteers (38 males and 19 females aged between 20 and 70) from a private addictology practice.

For each volunteer, alcohol use (AU) and Alcohol Use Disorders Identification Test (AUDIT) data was collected.

Also, finger-stick capillary blood samples were collected with Mitra (10 µL) microsampling devices to measure PEth levels using LC-MS/MS. A subset of the cohort (n = 21) was then tested for serum liver enzyme activity from standard venipuncture blood samples.

Alcohol Monitoring Study Findings

  • A good correlation (0.88) was observed when comparing AU and PEth levels in the blood samples.

  • There was a big difference in the PEth levels between those who were considered heavy drinkers consuming > 4 AU per day (PEth = 383.74±283.74 ng/ml) compared to those who were considered moderate drinkers consuming < 4 AU (PEth = 60.54±39.42ng/ml).

  • The average PEth level was 20% higher in females than males, which was correlated to the increased severity of the alcohol misuse in this cohort.

  • Very low correlation was observed between alcohol consumption and liver enzyme measurements. The correlation coefficients were estimated at 0.28 for GGT, 0.09 for AST and nothing for ALT.

  • These results confirmed findings of other studies, which showed that PEth was the only specific positive marker for alcoholism; the group concluded that biological markers such as live enzymes “provide little information” for the disease.

  • As discussed in the introduction, an issue associated with using liver enzymes is that they are not specific to monitoring alcohol abuse; hepatotoxic drugs and hepatitis can also cause an increase in liver enzymes. This issue was observed with two of the volunteers in this study, where the PEth was either negative or indicative of consumption of 4-6 AU per day but liver enzyme levels were elevated.

  • When conducting a study of alcohol withdrawal using data from an alcohol dependent patient (15 AU/day), the estimated half-life of PEth was 7.7 days. The PEth concentration reportedly fell to <1% after 52 days of abstinence. The group noted that other studies on alcohol withdrawal showed the half-life to be around 4-days.

  • The PEth assay offered a high sensitivity and specificity, leading the research group to state that PEth “provides clear answers in forensic situations where alcohol consumption is problematic.”

  • Stability of the PEth for samples stored at room temperature was shown to be 13% lower compared to samples stored at +4°C and -80°C. Further, the group said that the difference does not significantly alter the results of PEth measurements in practice.

PEth Study Authors’ Conclusions

PEth has proven to be a proportional and specific marker for alcohol consumption, with a long shelf life (~4-8 weeks). It can be used for understanding the real degree of alcohol consumption and so can be adapted to care and prevention of alcohol abuse.

PEth measurement using remote microsampling devices can be used for remote consultation as only a small drop of blood collected from a fingertip is needed. Finally, for those interested in pursuing forensic applications, PEth and the other tools described in the paper can be used as evidence.

Comments from Neoteryx, Trajan

The prevalence of alcoholism or alcohol abuse is a continuing problem for many societies, so having reliable tools and methods for measuring and monitoring alcohol misuse is critical. Until the discovery of PEth as a reliable direct biomarker for alcohol consumption, it had been challenging to obtain alcohol abuse data from individuals through blood tests. As outlined here, the use of other direct and indirect markers for monitoring alcohol use had various drawbacks, which led to challenges.

In today’s toxicology labs PEth is considered to be the most reliable long term alcohol marker and as confirmed by this study, it can be collected remotely using dried capillary microsampling. This allows more flexibility in how and where samples can be collected and by whom, negating the need for costly and often inconvenient phlebotomy blood draws in labs and other facilities.

This study paper was summarized for our readers by James Rudge, PhD, Microsampling Technical Director, Neoteryx. This is curated content. To learn more about the important research outlined in this review, visit the original article published in the World Journal of Biological and Pharmaceutical Research. 

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