VOUCHER-BASED REINFORCEMENT FOR ALCOHOL ABSTINENCE USING THE ETHYL-GLUCURONIDE ALCOHOL BIOMARKER

Introduction

  • Study on the effects of contingency management (CM) intervention for alcohol consumption.

  • Conducted by Michael G. McDonell and colleagues.

  • Target population: 10 alcohol-dependent participants.

Key Details of the Study

  • Design: ABCA design was implemented.

  • Methodology: Vouchers were contingent upon ethyl glucuronide (EtG) urine tests (alcohol biomarker with a 2-day detection window) and alcohol breath tests.

  • Results: Percentage of negative urines over study phases:

    • First baseline phase: 35%

    • C phase: 69%

    • Return-to-baseline phase: 20%

  • Conclusion: EtG urine tests are a feasible method to deliver CM and promote alcohol abstinence.

Background on Contingency Management (CM)

  • Definition: CM is an evidence-based approach that provides tangible rewards to reinforce desired behaviors; widely supported for promoting abstinence from illicit drugs (Prendergast et al., 2006).

  • Drug Testing: Use of low-cost immunoassay urine drug tests that provide immediate results for drug use typically detected up to 2 days prior to the test.

  • Current Issues in Alcohol CM: Previous findings supporting CM for alcohol use were limited due to breath tests that only detect use up to 12 hours (Warner & Sharma, 2009).

  • EtG Testing Advantages:

    • Ethyl glucuronide (EtG) is a metabolite of alcohol; urine detection of EtG can last up to 3 days (Litten et al., 2010).

    • Increasingly utilized in forensic, employment, and treatment contexts.

Research Methodology

Participants

  • Sample Size: 15 adults (aged 21-65, M=29, SD=8.8).

  • Eligibility Criteria:

    • Must meet criteria for alcohol dependence.

    • At least four drinking episodes each week (3+ drinks per episode in the prior 30 days).

  • Demographics:

    • Majority male (87%, n=13).

    • Predominantly Caucasian (80%, n=12).

    • Unemployed (67%, n=10).

  • Exclusion Criteria:

    • History of alcohol withdrawal.

    • Current methamphetamine use.

    • Unsafe to participate in the study.

Measures

  • Testing Frequency: Urine and breath samples collected at the initial intake and bi-weekly during 9 weeks.

  • EtG Testing:

    • Conducted by American Drug Testing, Spokane, WA, using a Microgenics MGC-240 analyzer.

    • Cutoff level: 500 ng/ml (Bottcher et al., 2008).

  • Alcohol Breath Tests:

    • Positive if BAC > 0.001%.

  • Self-report: Utilized the Timeline Followback (TLFB) for drinking assessment (Sobell & Sobell, 2000).

Procedure

  • Approval: Institutional Review Board approved the study.

  • Recruitment: Online advertisements targeted individuals with problematic alcohol and methamphetamine use history.

  • Screening Process:

    • 69 individuals responded, 45 screened over the phone, 29 eligible.

    • 15 provided consent and participated in the study procedures at Washington State University.

Study Design

  • ABCA Design:

    • A phases: Baseline (2 weeks).

    • B phase: Warning of upcoming contingencies (1 week).

    • C phase: CM intervention (4 weeks).

  • Reinforcement Schedule: Participants received $5 for each visit.

    • Vouchers based on negative results from urine and breath tests.

    • Subsequent visits increased voucher value by $2 for consecutive negative results.

    • Positive samples or no-shows reset voucher value.

  • Maximum Earnings: Up to $96 for continuous abstinence.

  • Final Session Requirement: Participants received motivational interviewing and referrals upon completion, and a $30 gift card for completing all visits.

Statistical Analysis

  • Used Generalized Estimating Equations (GEE) to assess CM effects on alcohol abstinence.

  • Analyzed outcomes comparing phases B and C against baseline phase.

  • Missing EtG samples were coded as positive; breath test data not statistically analyzed due to no positives.

  • TLFB data also analyzed via GEE with alpha set at .05.

  • Validity Measures: Sensitivity and specificity calculated for EtG-I tests and compared against TLFB as the standard.

Results and Discussion

  • Submission of Negative Samples:

    • 9/15 participants had alcohol-negative EtG-I samples at intake.

    • 2 participants didn’t complete baseline phase; 3 were abstinent during baseline and sobriety warning phases.

    • Remaining participants showed significant changes in urine tests across study phases:

    • Baseline: 35%

    • B phase: 60%

    • C phase: 69%

    • Return-to-baseline: 20%

  • Odds Ratio Results:

    • CM phase (C) significantly increased likelihood of negative urine samples compared to baseline (Odds Ratio = 4.71, p < .05).

  • Self-reports via TLFB:

    • Abstinence rates: Baseline (37%), Sobriety Warning (65%), CM phase (63%), Return to Baseline (43%); notable increases during the sobriety warning and CM phases (p < .05).

  • Average Earnings: Participants averaged $77 (SD = $27) during CM phase.

  • Agreement between EtG-I and TLFB: 74% agreement on self-reported drinking at least 2 standard drinks over 2 days prior to urine collection.

  • Sensitivity and Specificity of EtG-I:

    • Sensitivity: 75% for drinking 1 day prior, 50% for 2 days prior.

    • Specificity: High at 97%, disproving prior concerns over false positives from incidental ethanol ingestion.

Limitations of the Study

  • Potential influence of breath test administration on participant behavior.

  • Need for larger studies for robust EtG-I accuracy evaluation.

  • Small sample size limits conclusions.

  • Future research should investigate on-site analyzers for accurate immediate feedback on EtG levels.

Conclusion

  • Recommendations for further investigations into the feasibility and effectiveness of CM interventions based on EtG-I testing for alcohol abstinence are necessary, especially regarding cost-effective on-site solutions.