High levels of agreement between clinic-based ethyl glucuronide (EtG) immunoassays and laboratory-based mass spectrometry

Alcohol use and HIV suppression after completion of financial incentives for alcohol abstinence and isoniazid adherence: a randomized controlled trial

Background

In a recent randomized trial, six months of financial incentives contingent for recent alcohol abstinence led to lower levels of hazardous drinking, while incentives for recent isoniazid (INH) ingestion had no impact on INH adherence, during TB preventive therapy among persons with HIV (PWH). Whether the short-term incentives influence long-term alcohol use and HIV viral suppression post-intervention is unknown.

Methods

We analyzed twelve-month HIV viral suppression and alcohol use in the Drinkers' Intervention to Prevent Tuberculosis study, a randomized controlled trial among PWH with latent TB and unhealthy alcohol use in south-western Uganda. We randomly assigned 680 participants (1:1:1:1) initiating six months of INH to: Arm 1, no incentives (control); Arm 2, financial incentives contingent on recent alcohol abstinence; Arm 3, incentives contingent on recent INH use; and Arm 4, incentives for recent alcohol abstinence and INH use, rewarded separately. The 6 months post-intervention outcomes evaluated were pre-specified and included: HIV viral suppression (<200 copies/mL) and no/low alcohol use, defined as Alcohol Use Disorders Identification Test-Consumption negative (<3: women, <4: men) and phosphatidylethanol, an alcohol biomarker, <35 ng/mL. We estimated adjusted risk differences (aRD) for alcohol reduction and INH adherence interventions using multivariable logistic regression adjusting for randomization stratification factors (sex and study site), and baseline alcohol use (alcohol intervention model only). Clinicaltrials.gov registration: NCT03492216, Registered 04/10/2018.

Findings

Of 600 participants with 12-month viral load results, 556/585 (95%) with baseline results were virally suppressed, and 583/600 (97%) were virally suppressed at 12-months. Twelve-month viral suppression did not differ significantly between either intervention group versus control (alcohol reduction incentives versus control aRD = -0.9% (95% CI: -3.6 to 1.7); INH adherence incentives versus control aRD = 2.2% (95% CI: -0.4 to 4.9)). Of the 617 participants with 12-month alcohol use measures, alcohol reduction incentives led to a significantly greater proportion with no/low alcohol use at 12-months (20.2% [64/317]) versus no alcohol reduction incentives (11.0% [33/300]); aRD = 8.4%, (95% CI: 3.3-13.4), p = 0.001.

Interpretation

Viral suppression was high (>95%) at baseline and at 12 months: we found no effect of either 6-month alcohol reduction or INH adherence incentives on long-term viral suppression. Six months of alcohol reduction incentives were effective at promoting no/low alcohol use at 12 months, demonstrating persistent effects post-intervention.

Funding

National Institutes of Health (NIH/NIAAA) U01AA026223 (PI: Hahn) and U01AA026221 (PI: Chamie), NIH/NIAAAK24 AA022586 (PI: Hahn), NIH/NIAAAK24 AA031211 (PI: Chamie), Providence/Boston Center for AIDS ResearchP30AI042853 (PI: Sara Lodi).

A Review of Drug Abuse, Misuse, and Related Laboratory Challenges

Various definitions can be considered for drugs and substance abuse. According to the National Institute on Abuse, the use of an over-the-counter drug in a different way than that prescribed to experience or arouse emotion is a simple form of drug abuse. The World Health Organization (WHO) also defines drug abuse as the persistent or sporadic use of drugs that are incompatible or unrelated to acceptable medical practice. With the increasing non-therapeutic use of prescription drugs, serious related consequences have also increased. Therefore, there is a need to know more precisely about the types of substances and drug abuse, which is the most important part of diagnosis and recognizing the tests that cause false positive and negative results. The purpose of this review article is to collect and summarize the most important and more common types of drugs of abuse and review the drugs that cause false results in screening tests. In addition, the most common detection methods of the drug will be reviewed and the advantages and drawbacks of each method will be discussed. In this article, we aimed to point out all the facts about the emerging problems in drug abuse, the methods of screening, and the possible false results in addition to troubleshooting strategies.

[Problems of ethyl glucuronide use in ethanol consumption diagnosis]

Quantitative determination of ethyl glucuronide (EtG) in different biological objects in recent years has been positioned as one of the most reliable biomarkers of unconditional alcohol consumption. The aim of the study is to summarize the analytical methods of alcohol consumption testing with the use of EtG currently available in domestic and foreign literature and to present a schematic overview of possible errors in reproducibility and interpretation of research on EtG results, which may limit their use in forensic medical practice. The main objective is to increase the reliability and validity of EtG as a marker of ethanol consumption.

Alcohol Cue Processing in Co-Occurring Bipolar Disorder and Alcohol Use Disorder

Importance

Reward circuitry dysfunction is a candidate mechanism of co-occurring bipolar disorder and alcohol use disorder (BD + AUD) that remains understudied. This functional magnetic resonance imaging (fMRI) research represents the first evaluation of alcohol cue reward processing in BD + AUD.

Objective

To determine how alcohol cue processing in individuals with BD + AUD may be distinct from that of individuals with AUD or BD alone.

Design, Setting, and Participants

This cross-sectional case-control study (April 2013-June 2018) followed a 2 × 2 factorial design and included individuals with BD + AUD, AUD alone, BD alone, and healthy controls. A well-validated visual alcohol cue reactivity fMRI paradigm was administered to eligible participants following their demonstration of 1 week or more of abstinence from alcohol and drugs assessed via serial biomarker testing. Study procedures were completed at the Medical University of South Carolina. Analysis took place between June and August 2022.

Main Outcomes and Measures

Past-week mood symptoms were rated by clinicians using the Montgomery-Åsberg Depression Rating Scale and Young Mania Rating Scale. The Alcohol Dependence Scale, Obsessive-Compulsive Drinking Scale, and Barratt Impulsiveness Scale were included questionnaires. Functional MRI whole-brain data were analyzed along with percent signal change within a priori regions of interest located in the ventral striatum, dorsal striatum, and ventromedial prefrontal cortex. Exploratory analyses of associations between cue reactivity and select behavioral correlates (alcohol craving, impulsivity, maximum number of alcohol drinks on a single occasion, and days since last alcohol drink) were also performed.

Results

Of 112 participants, 28 (25.0%) had BD + AUD, 26 (23.2%) had AUD alone, 31 (27.7%) had BD alone, and 27 (24.1%) were healthy controls. The mean (SD) age was 38.7 (11.6) years, 50 (45.5%) were female, 33 (30%) were smokers, and 37 (34.9%) reported recent alcohol consumption. Whole-brain analyses revealed a BD × AUD interaction (F = 10.64; P = .001; η2 = 0.09) within a cluster spanning portions of the right inferior frontal gyrus and insula. Region of interest analyses revealed a main association of BD (F = 8.02; P = .006; η2 = 0.07) within the dorsal striatum. In each instance, individuals with BD + AUD exhibited reduced activation compared with all other groups who did not significantly differ from one another. These hypoactivations were associated with increased impulsivity and obsessive-compulsive alcohol craving exclusively among individuals with BD + AUD.

Conclusion and Relevance

The findings of this study suggest conceptualizing reward dysfunction in BD + AUD by the potential interaction between blunted reward responsivity and deficient inhibitory control may help guide treatment development strategies. To this end, reduced right inferior frontal gyrus and insula alcohol cue reactivity represents a novel candidate biomarker of BD + AUD that may respond to pharmacological interventions targeting impulsivity-related neural mechanisms for improved executive control.

Investigating Secondary Alcohol Outcomes in a Contingency Management Intervention among American Indian and Alaska Native Adults

OBJECTIVE

The aim of the study is to investigate clinically meaningful, secondary outcomes in a randomized trial of a culturally adapted contingency management (CM) intervention for alcohol use in 3 diverse American Indian and Alaska Native communities.

METHODS

Three American Indian and Alaska Native communities located in the Northern Plains, Alaska, and the Inland Northwest were partnering sites. A total of 158 individuals were randomized to either a 12-week CM intervention or a noncontingent (NC) control group. The CM group received reinforcers for providing alcohol-negative ethyl glucuronide (EtG < 150 ng/mL) urine samples, while the NC group received reinforcers unconditionally. Outcomes included EtG as a continuous measure (range, 0-2,000 ng/mL), EtG > 499 ng/mL (a measure of higher levels of recent alcohol use), longest duration of abstinence, and time-to-first alcohol-positive EtG during the trial. Generalized estimating equations along with Cox proportional hazard and negative binomial regressions were used.

RESULTS

Participants randomized to the CM group had lower mean EtG levels (-241.9 ng/mL; 95% confidence interval [CI], -379.0 to -104.8 ng/mL) and 45.7% lower odds (95% CI, 0.31 to 0.95) of providing an EtG sample indicating higher levels of alcohol use during the intervention. Longest duration of abstinence was 43% longer for the CM group than the NC group (95% CI, 1.0 to 1.9). Risk of time-to-first drink during treatment did not differ significantly.

CONCLUSIONS

These secondary outcome analyses provide evidence that CM is associated with reductions in alcohol use and longer durations of abstinence (as assessed by EtG), both clinically meaningful endpoints and analyses that differ from the primary study outcome.

Cultural Factors and Alcohol Use in American Indian Adults: Results From a Culturally Tailored Contingency Management Intervention

OBJECTIVE

American Indian and Alaska Native (AI/AN) populations experience greater health disparities in alcohol use outcomes compared with the general population. This secondary data analysis examines cultural factors related to alcohol use in reservation-based American Indian (AI) adults (N = 65; 41 males; mean age = 36.7 years) in a randomized controlled trial of a culturally tailored contingency management (CM) program. It was hypothesized that individuals with higher rates of cultural protective factors would have lower rates of alcohol use, whereas individuals with higher rates of risk factors would have higher rates of alcohol use. It was also hypothesized that enculturation would moderate the relationship between treatment group and alcohol use.

METHOD

Generalized linear mixed modeling was used to calculate odds ratios (ORs) for the repeated measure, biweekly urine tests of the biomarker, ethyl glucuronide (EtG), across 12 weeks. The relationships between alcohol use (abstinence [EtG < 150 ng/ml]) or heavy drinking [EtG > 500 ng/ml]) and culturally relevant protective (enculturation, years lived on the reservation) and risk factors (discrimination, historical loss, historical loss symptoms) were examined.

RESULTS

There was a negative association between enculturation and probability of submitting a heavy drinking urine sample (OR = 0.973; 95% CI [0.950, 0.996], p = .023), indicating that enculturation may serve as a protective factor against heavy drinking.

CONCLUSIONS

Cultural factors (e.g., enculturation) may be important constructs to assess and incorporate into treatment planning with AI adults engaged in alcohol treatment.

What the lab can and cannot do: clinical interpretation of drug testing results

Urine drug testing is one of the objective tools available to assess adherence. To monitor adherence, quantitative urinary results can assist in differentiating "new" drug use from "previous" (historical) drug use. "Spikes" in urinary concentration can assist in identifying patterns of drug use. Coupled chromatographic-mass spectrometric methods are capable of identifying very small amounts of analyte and can make clinical interpretation rather challenging, specifically for drugs that have a longer half-life. Polypharmacy is common in treatment and rehabilitation programs because of co-morbidities. Medications prescribed for comorbidities can cause drug-drug interaction and phenoconversion of genotypic extensive metabolizers into phenotypic poor metabolizers of the treatment drug. This can have significant impact on both pharmacokinetic (PK) and pharmacodynamic properties of the treatment drug. Therapeutic drug monitoring (TDM) coupled with PKs can assist in interpreting the effects of phenoconversion. TDM-PKs reflects the cumulative effects of pathophysiological changes in the patient as well as drug-drug interactions and should be considered for treatment medications/drugs used to manage pain and treat substance abuse. Since only a few enzyme immunoassays for TDM are available, this is a unique opportunity for clinical laboratory scientists to develop TDM-PK protocols that can have a significant impact on patient care and personalized medicine. Interpretation of drug screening results should be done with caution while considering pharmacological properties and the presence or absence of the parent drug and its metabolites. The objective of this manuscript is to review and address the variables that influence interpretation of different drugs analyzed from a rehabilitation and treatment programs perspective.

Pilot investigation: randomized-controlled analog trial for alcohol and tobacco smoking co-addiction using contingency management

Contingency management (CM) is associated with decreases in off-target drug and alcohol use during primary target treatment. The primary hypothesis for this trial was that targeting alcohol use or tobacco smoking would yield increased abstinence in the opposite, nontargeted drug. We used a 2 [CM vs. noncontingent control (NC) for alcohol]×2 (CM vs. NC for smoking tobacco) factorial design, with alcohol intake (through urinary ethyl glucuronide) and tobacco smoking (through urinary cotinine) as the primary outcomes. Thirty-four heavy-drinking smokers were randomized into one of four groups, wherein they received CM, or equivalent NC reinforcement, for alcohol abstinence, smoking abstinence, both drugs, or neither drug. The CM for alcohol and tobacco group had only two participants and therefore was not included in analysis. Compared with the NC for alcohol and tobacco smoking group, both the CM for the tobacco smoking group [odds ratio (OR)=12.03; 95% confidence interval (CI): 1.50-96.31] and the CM for the alcohol group (OR=37.55; 95% CI: 4.86-290.17) submitted significantly more tobacco-abstinent urinalyses. Similarly, compared with the NC for the alcohol and tobacco group, both the CM for smoking (OR=2.57; 95% CI: 1.00-6.60) and the CM for alcohol groups (OR=3.96; 95% CI: 1.47-10.62) submitted significantly more alcohol-abstinent urinalyses. These data indicate cross-over effects of CM on indirect treatment targets. Although this is a pilot investigation, it could help to inform the design of novel treatments for alcohol and tobacco co-addiction.

Point-of-Care Urine Ethyl Glucuronide Testing to Detect Alcohol Use Among HIV-Hepatitis B Virus Coinfected Adults in Zambia

In an HIV-hepatitis B virus (HIV-HBV) coinfection cohort in Zambia, we piloted a qualitative point-of-care (POC) test for urine Ethyl glucuronide (uEtG), assessed concordance between uEtG and alcohol use disorders identification test-consumption (AUDIT-C), and identified epidemiological factors associated with underreporting (defined as uEtG-positivity with last reported drink > 7 days prior). Among 211 participants (40.8% women), there were 44 (20.8%) lifetime abstainers, 32 (15.2%) former drinkers, and 135 (64.0%) current drinkers, including 106 (50.2%) with unhealthy drinking per AUDIT-C. Eighty-seven (41.2%) were uEtG-positive including 64 of 65 (98.5%) who drank ≤ 3 days prior and 17 of 134 (12.7%) underreported, all of whom admitted to recent drinking when results were discussed. uEtG was moderately concordant with AUDIT-C. Past drinking (versus lifetime abstinence) and longer time on antiretrovirals (≥ 12 months) were associated with underreporting. These data support further use of POC alcohol biomarkers in HIV and hepatitis research and clinical settings.

Monitoring people at risk of drinking by a rapid urinary ethyl glucuronide test

Alcohol and illicit drug abuse are major public health problems worldwide. Since alcohol is the predominant substance of choice in polydrug abusers, monitoring its use, along with urinary drug screening in patients in rehabilitation programs, appeared to be crucial in identifying patients at risk of alcohol disorders leading to impaired quality of life. Ethyl β-D-6-glucuronide, a non-oxidative, non-volatile, stable and minor direct ethanol metabolite, has a 6h to 4 day window of detection in urine after the last alcohol intake. Each of the 119 subjects (85 males, 34 females) registered with the Public Health Service for Drug Dependence Treatment provided a urine sample for ethylglucoronide (EtG) determination in an immunochemical test with a 500 ng/ml cutoff. All results were evaluated with confirmation criteria of a fully validated gas chromatography/mass spectrometry assay. The diagnostic performance of the EtG immunochemical test was assessed using Receiver Operating Characteristic Curve analysis. The immunochemical test specificity was 100% for EtG urinary values above 500 ng/ml. No false positive results were found. With levels below 500 ng/ml, 12% of the samples were classified as negative. The average consumption of the incorrectly classified subjects was 171 ng/ml, with a misclassification error of 6.5% to 18.5%. High agreement between EtG as determined in an immunochemical test and gas chromatography/mass spectrometry, suggests that the rapid EtG test is a reliable, cost-effective alcohol monitoring assay for patient management in many non-forensic settings, such as drug rehabilitation programs.

Clinical Interpretation of Urine Drug Tests: What Clinicians Need to Know About Urine Drug Screens

Urine drug testing is frequently used in clinical, employment, educational, and legal settings and misinterpretation of test results can result in significant adverse consequences for the individual who is being tested. Advances in drug testing technology combined with a rise in the number of novel misused substances present challenges to clinicians to appropriately interpret urine drug test results. Authors searched PubMed and Google Scholar to identify published literature written in English between 1946 and 2016, using urine drug test, screen, false-positive, false-negative, abuse, and individual drugs of abuse as key words. Cited references were also used to identify the relevant literature. In this report, we review technical information related to detection methods of urine drug tests that are commonly used and provide an overview of false-positive/false-negative data for commonly misused substances in the following categories: cannabinoids, central nervous system (CNS) depressants, CNS stimulants, hallucinogens, designer drugs, and herbal drugs of abuse. We also present brief discussions of alcohol and tricyclic antidepressants as related to urine drug tests, for completeness. The goal of this review was to provide a useful tool for clinicians when interpreting urine drug test results and making appropriate clinical decisions on the basis of the information presented.

A Randomized Controlled Trial of Ethyl Glucuronide-Based Contingency Management for Outpatients With Co-Occurring Alcohol Use Disorders and Serious Mental Illness

OBJECTIVE

The authors examined whether a contingency management intervention using the ethyl glucuronide (EtG) alcohol biomarker resulted in increased alcohol abstinence in outpatients with co-occurring serious mental illnesses. Secondary objectives were to determine whether contingency management was associated with changes in heavy drinking, treatment attendance, drug use, cigarette smoking, psychiatric symptoms, and HIV-risk behavior.

METHOD

Seventy-nine (37% female, 44% nonwhite) outpatients with serious mental illness and alcohol dependence receiving treatment as usual completed a 4-week observation period and were randomly assigned to 12 weeks of contingency management for EtG-negative urine samples and addiction treatment attendance, or reinforcement only for study participation. Contingency management included the variable magnitude of reinforcement "prize draw" procedure contingent on EtG-negative samples (<150 ng/mL) three times a week and weekly gift cards for outpatient treatment attendance. Urine EtG, drug test, and self-report outcomes were assessed during the 12-week intervention and 3-month follow-up periods.

RESULTS

Contingency management participants were 3.1 times (95% CI=2.2-4.5) more likely to submit an EtG-negative urine test during the 12-week intervention period, attaining nearly 1.5 weeks of additional alcohol abstinence compared with controls. Contingency management participants had significantly lower mean EtG levels, reported less drinking and fewer heavy drinking episodes, and were more likely to submit stimulant-negative urine and smoking-negative breath samples, compared with controls. Differences in self-reported alcohol use were maintained at the 3-month follow-up.

CONCLUSIONS

This is the first randomized trial utilizing an accurate and validated biomarker (EtG) to demonstrate the efficacy of contingency management for alcohol dependence in outpatients with serious mental illness.

A culturally-tailored behavioral intervention trial for alcohol use disorders in three American Indian communities: Rationale, design, and methods

BACKGROUND

Disproportionately high rates of alcohol use disorders are present in many American Indian/Alaska Native (AI/AN) communities, yet little information exists regarding the effectiveness of alcohol treatments in AI/AN populations. Contingency management is an intervention for illicit drug use in which tangible reinforcers (rewards) are provided when patients demonstrate abstinence as assessed by urine drug tests. Contingency management has not been widely studied as an intervention for alcohol problems because until recently, no alcohol biomarker has been available to adequately verify abstinence.

AIMS

The HONOR Study is designed to determine whether a culturally-tailored contingency management intervention is an effective intervention for AI/AN adults who suffer from alcohol use disorders.

METHODS

Participants include 400 AI/AN alcohol-dependent adults residing in one rural reservation, one urban community, as well as a third site to be decided, in the Western U.S. Participants complete a 4-week lead-in phase prior to randomization, then 12 weeks of either a contingency management intervention for alcohol abstinence, or a control condition where participants receive reinforcers for attending study visits regardless of alcohol use. Participants are then followed for 3-more months post-intervention. The primary study outcome is urinary ethyl glucuronide-confirmed alcohol abstinence; secondary outcomes include self-reported alcohol and drug use, HIV risk behaviors, and self-reported cigarette smoking.

DISCUSSION

This will be the largest randomized, controlled trial of any alcohol for AI/ANs and the largest contingency management study targeting alcohol use disorders, thus providing important information to AI/AN communities and the alcohol treatment field in general.

Using ethyl glucuronide in urine to detect light and heavy drinking in alcohol dependent outpatients

AIMS

This study investigated which ethyl glucuronide immunoassay (EtG-I) cutoff best detects heavy versus light drinking over five days in alcohol dependent outpatients.

METHODS

A total of 121 adults with alcohol use disorders and co-occurring psychiatric disorders took part in an alcohol treatment study. Participants provided self-reported drinking data and urine samples three times per week for 16-weeks (total samples=2761). Agreement between low (100 ng/mL, 200 ng/mL), and moderate (500 ng/mL) EtG-I cutoffs and light (women ≤3 standard drinks, men ≤4 standard drinks) and heavy drinking (women >3, men >4 standard drinks) were calculated over one to five days.

RESULTS

The 100 ng/mL cutoff detected >76% of light drinking for two days, and 66% at five days. The 100 ng/mL cutoff detected 84% (1 day) to 79% (5 days) of heavy drinking. The 200 ng/mL cutoff detected >55% of light drinking across five days and >66% of heavy drinking across five days. A 500 ng/mL cutoff identified 68% of light drinking and 78% of heavy drinking for one day, with detection of light (2-5 days <58%) and heavy drinking (2-5 days <71%) decreasing thereafter. Relative to 100 ng/mL, the 200 ng/mL and 500 ng/mL cutoffs were less likely to result in false positives.

CONCLUSIONS

An EtG-I cutoff of 100 ng/mL is most likely to detect heavy drinking for up to five days and any drinking during the previous two days. Cutoffs of ≥500 ng/mL are likely to only detect heavy drinking during the previous day.

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.

Determining ethyl glucuronide cutoffs when detecting self-reported alcohol use in addiction treatment patients

BACKGROUND

Ethyl glucuronide (EtG) is an alcohol biomarker with potential utility as a clinical research and alcohol treatment outcome. Debate exists regarding the appropriate cutoff level for determining alcohol use, particularly with the EtG immunoassay. This study determined the EtG immunoassay cutoff levels that most closely correspond to self-reported drinking in alcohol-dependent outpatients.

METHODS

Eighty adults with alcohol dependence and mental illness, taking part in an alcohol treatment study, provided urine samples 3 times per week for up to 16 weeks (1,589 samples). Self-reported drinking during 120 hours prior to each sample collection was assessed. Receiver operating characteristic analyses were conducted to assess the ability of the EtG immunoassay to detect self-reported alcohol use across 24- to 120-hour time periods. Sensitivity and specificity of EtG immunoassay cutoff levels was compared in 100 ng/ml increments (100 to 500 ng/ml) across 24 to 120 hours.

RESULTS

Over half (57%) of the 1,589 samples indicated recent alcohol consumption. The EtG immunoassay closely corresponded to self-reported drinking from 24 (area under the curve [AUC] = 0.90, 95% confidence interval [CI]: 0.88, 0.92) to 120 hours (AUC = 0.88, 95% CI: 0.87, 0.90). When cutoff levels were compared across 24 to 120 hours, 100 ng/ml had the highest sensitivity (0.93 to 0.78) and lowest specificity (0.67 to 0.85). Relative to 100 ng/ml, the 200 ng/ml cutoff demonstrated a reduction in sensitivity (0.89 to 0.67), but improved specificity (0.78 to 0.94). The 300, 400, and 500 ng/ml cutoffs demonstrated the lowest sensitivity (0.86 to 0.33) and highest specificity (0.86 to 0.97) over 24 to 120 hours.

CONCLUSIONS

For detecting alcohol use for >24 hours, the 200 ng/ml cutoff level is recommended for use as a research and clinical outcome.