1. Fingernail and Hair Ethyl Glucuronide as a Long-Term Alcohol Biomarker
L. Berger1, M. Fendrich1, D. Fuhrmann1, C. Plate2, D. Lewis2, J. Jones2
1Center for Addiction and Behavioral Health Research, Helen Bader School of Social Welfare, University of Wisconsin-Milwaukee
2United States Drug Testing Laboratories, Des Plaines, Illinois
INTRODUCTION
Alcohol biomarkers can have utility in clinical and research settings and in public safety applications[1] such as possible assessment of risk when relicensing DUI offenders[2].
Newer alcohol biomarkers such as ethyl glucuronide (EtG) represent a departure from older alcohol biomarkers in their ability to directly detect alcohol versus indirectly detect possible health consequences of alcohol use[3].
The purpose of this study was to examine fingernail and hair EtG as a long-term, up to 90-day, alcohol biomarker.
METHODS
Study Design, Sample, and Procedures
Probability sample of undergraduate college students
18-25 years of age at recruitment and enrolled in both the spring and summer, 2010 semesters at a public, urban university
Participants completed a confidential interview and self-administered web-based survey focused on alcohol use and related behaviors
Following the survey, interviewers collected a sample of hair from the crown of the head, and participants clipped their own fingernails
Data were collected from July-October, 2010*
Measures
Sociodemographics, the Timeline Followback for past 90 days of alcohol use[4] as measured in standard drinks[5], and chemical treatment of hair (bleached, dyed, permed, or chemically straightened) in the past 90 days
Data Analysis
Descriptives and logistic regression analysis
A positive EtG fingernail test was ≥ 20 picograms/ milligram (pg/mg)[6]
A positive hair EtG test was ≥ 30 pg/mg, which strongly suggests chronic excessive alcohol use[7]
RESULTS
Sample Characteristics: The sample was comprised of 606 participants; study response rate was 54%[8]. Participants were mostly female (62%), upperclassmen (62%), and white (82%); average age was 22 years old (SD=1.67).
Fingernail and Hair EtG Unadjusted Models: Logistic regression analysis revealed that total number of standard drinks in the past 90 days was significantly associated with a positive fingernail EtG test (β = 0.016, p < .001), and likewise, a positive hair EtG test (β = 0.008, p < .001). Figures 1a and 1b display the areas under the ROC curve (AUC) for the unadjusted models (Drinks_ Past90).
Fingernail and Hair EtG Adjusted Models: Logistic regression analysis that controlled for age, gender, and race revealed that total number of standard drinks in the past 90 days was significantly associated with a positive fingernail EtG test (β = 0.017, p < .001), and likewise, a positive hair EtG test (β = 0.007, p < .001). Figures 1a and 1b display the AUC for the adjusted models.
Hair EtG and Chemical Treatment of Hair: In a final logistic regression model that controlled for chemical treatment of hair, total number of standard drinks in the past 90 days was significantly associated with a positive hair EtG test (β = 0.008, p < .001) while past 90-day chemical treatment of hair was significantly associated with a reduced probability of a positive test (β = -1.73, p < .01).
Positive Fingernail and Hair EtG Tests: Based on cross tabular analysis, 41 out of 47 positive hair tests were also positive fingernail tests (TPR=0.87, 95% CI [0.74,0.95]) while 347 out of 484 negative hair tests were also negative nail tests (TNR=0.72, 95% CI [0.68,0.76]).
RESULTS (CONT.)
DISCUSSION
At currently used cut-off points, EtG in both fingernails and hair may have utility as a long-term, up to 90-day, alcohol biomarker. Chemical treatment of hair (e.g., bleaching) may reduce the probability of a positive hair EtG test but does not change the magnitude of the association between total number of standard drinks in the past 90 days and a positive hair test.
Although total number of standard drinks in the past 90 days was significantly associated with both a positive fingernail and hair EtG test, further investigation is needed to determine the patterns of drinking in a 90-day period that will result in a positive test.
Fingernails may be a more sensitive matrix than hair for detecting alcohol consumption, and further research linking various behavioral alcohol consumption reports will be conducted to evaluate this finding.
Finally, EtG in some applications is still considered experimental at this time[3].
REFERENCES
Available as a handout from the authors.
Frequencies of Test Results
Hair EtG Test
Fingernail EtG Test - +
Total
347 6
353
137 41
178
484 47
531
ACKNOWLEDGEMENTS: This study was funded by the National Institute on Alcohol Abuse and Alcoholism (R44AA016463).
*Data collection was performed by the University of Wisconsin Survey Center under the supervision of Project Director Jessica Price.
CONTACT INFORMATION
Michael Fendrich, PhD
University of Wisconsin-Milwaukee
Center for Addiction and Behavioral Health Research
Helen Bader School of Social Welfare
2400 E. Hartford Avenue, Milwaukee, WI