ABSTRACT. The risk of impaired driving can be estimated through the use of several technologies but few programs utilize the full spectrum of predictive ...
T2007 – Seattle, Washington
DUI risk prediction with alcohol biomarkers, interlock records, and self-report. Paul Marques*1, Martin Javors2, Fritz Pragst3, Volker Auwaerter3, Steina Aradottir4, Christer Alling4, Michel Yegles5, Friedrich Wurst6 PIRE, Calverton, MD USA, 2Univ. Texas, San Antonio, TX USA; 3Inst Legal Medicine Humboldt Univ. Berlin, Germany; 4Dept. Medical Neurochemistry Lund Univ. Sweden; 5Nat’l Lab of Health Univ. Luxembourg; 6Paracelsus Medical Univ. Salzburg, Austria. 1
ABSTRACT The risk of impaired driving can be estimated through the use of several technologies but few programs utilize the full spectrum of predictive technologies and often underutilize the ones they do employ. The record of alcohol ignition interlock breath alcohol (BAC) tests are good predictors of future DUI risk, but still not widely used. These are a good, but imperfect predictor, since drivers other than the DUI offender of record can use the interlock car. Biological markers of alcohol use can more directly target the impairment risk of specific individuals. Use of biomarkers to monitor progress among DUI offenders is growing in Europe but less so in North America. A sample of 537 interlock using DUI offenders from Alberta, Canada have been providing self-report assessments as well as biological specimens at two time points, the beginning of an interlock installation, and typically 6 months later, to determine: a) the predictive relationship between the biomarkers and the record of interlock BAC tests, b) the cross-relationship among the biomarkers, c) the relationship between the biomarkers and self-report assessments, and d) the extent to which the markers, self-report, and interlock BAC tests can correctly predict future (post-interlock) recidivism. Biomarkers under study include conventional alcohol markers such as GGT, ALT, AST, MCV, and percent carbohydrate deficient transferrin (%CDT), but also markers that directly reflect ethanol consumption such phosphatidyl ethanol (PEth), fatty acid ethyl esters (FAEE), and ethyl glucuronide (EtG). Self-report assessments include AUDIT, Drinker Inventory of Consequences (Drinc), the DSM4 Alcohol Dependence assessment from the DIS-C, and Timeline Followback (TLFB) and Temptation Restraint Inventory (TRI). Interlock BAC test data are represented as a proportion of all tests taken that are elevated above .02 g/dL over the full six months as well as for each 2 month interval since installation. Preliminary results show many markers correlate significantly and all in the right direction with interlock BAC tests and self-report indicators. TLFB self-report variables (such as % drinking days, drinks per week) show significant correlations (Spearman and Pearson) with markers and BAC tests. Direct markers, especially PEth, EtG and FAEE, but also GGT, are significantly related to the proportion of elevated interlock BAC tests. Sample size is variable across measures, but continues to grow; post-interlock subsequent DUI events will also grow, but currently with just 9 repeat DUI events there are too few for predictive profiling. Biomarkers are an important monitoring tool and should be used as a supplement to conventional estimates of driver risk. These should be more widely utilized especially in conjunction with alcohol harm reduction or medical interventions. Keywords: biomarkers, interlock, alcohol, DUI
INTRODUCTION Developed societies search for better ways to identify and control alcohol impaired drivers. A risk profile can be roughly estimated such that higher arrest BAC and more arrests pose greater public risk, but such groups are only a small part of the problem, While drivers with a BAC ≥.15 g/dL do account for 61-65% of the fatally injured drinking drivers (Williams, McCartt & Ferguson, 2007), fatalities are an incomplete risk criterion. Drivers with lower BACs account for the largest proportion of alcohol injury crashes partly because there are so many more people contributing to the problem. Even in Australia where random breath testing (RBT) makes an important contribution to general deterrence, and in Queensland where the average driver is tested randomly every year, about half of tested drivers report continuing to drink and drive occasionally (Watson and Freeman, 2007). Ignition interlocks, which require a breath test before each start up, reduce recidivism approximately 64% among those who install interlocks (Willis et al., 2005;Voas et al., 1999), but low uptake rates (typically under 10%) continues to be a barrier to real effectiveness (Voas & Marques, 2003). Based on available data, the most effective interlock program is New Mexico where the interlock is a requirement for all drivers convicted of DUI and also allows for previously revoked offenders to drive an interlock car. Nonetheless New Mexico still only gets about half of the offenders onto the interlock. In a strict mandatory interlock program that used home confinement as an alternative to the interlock, Hancock County, Indiana’s strong sanction achieved 62% installation (Voas et al., 2002), which still left 38% without interlocks. There are several reasons that even in mandatory interlock states, not all DUI offenders get an interlock. Judges are often reluctant to require interlocks if offenders claim to have no car, or if they claim to have no need for a driver license. These would be reasonable exceptions if true, but evidence from many jurisdictions over many years has demonstrated that a suspended or revoked driver license is no barrier to driving (just as having an interlock car carries no guarantee of its being used). And even with a 1 or 2 year interlock sentence, once the interlock is removed many offenders return to their previous rates of impaired driving. The result is that interlocks can prevent impaired driving, if used as intended, but they do not permanently change behavior (as currently implemented) or substantially reduce the predilection for drinking-driving. There are ways evaluate alcohol use status of high risk drivers but none have been tested comprehensively. An offender can claim to not have a car and perhaps thereby avoid an interlock requirement, but we all have blood, sweat, urine, saliva, hair and other body matrices that can be used to evaluate exposure to alcohol or other drugs. Researchers and program developers are not restricted to archival driving records for gathering data and forming opinions about the risk presented by drivers who repeatedly endanger the public. Evaluation of alcohol (or drugs) in body matrices, either as a measure of impairment or habitual use, could be employed as a means of monitoring compliance with court orders for those who prove themselves unwilling to alter the behavior – impaired driving – that poses a roadway risk. This research report is a preliminary evaluation of the way in which several alcohol biomarkers found in the blood, urine and hair of convicted DUI offenders can be shown to interrelate with both self-reported consumption of alcohol as well as the breath test data logged in the ignition interlock recorder. We have demonstrated in our prior publications (Marques et al., 2001, 2003a, 2003b) that the breath test record of the ignition interlock is an early proxy/predictor of future repeat DUI risk. In this report we use the breath test record from the interlock as a criterion, an
objective risk outcome measure, to serve as a target for the alcohol biomarker predictors measured in samples provided by the offender. Alcohol biomarkers such as CDT (carbohydrate deficient transferrin), GGT (gamma glutamyl transferase), MCV (macrocytic or red cell volume), AST (aspartate aminotransferase) and ALT (alanine aminotransferase), are often used by alcohol rehabilitation physicians to monitor dependence treatment and can be usefully employed for monitoring driver fitness (Bjerre, 2005; Appenzeller et al., 2005). Recent work by Bjerre and co-workers have shown how the use of medical monitoring with alcohol biomarkers as part of a comprehensive alcohol interlock program can even reduce hospitalization costs and sick days (Bjerre et al., 2007), and presumably public risk exposure from those drivers. Beyond the widely used markers of alcohol dependence, another class of alcohol markers directly reflects consumption level but can be measured in circulation or in urine for several days after BAC has returned to zero, and can be found in the hair for months. Direct markers such as ethyl glucuronide (EtG) and ethyl sulfate (EtS) (Wurst et al, 2003) and fatty acid ethyl esters (FAEE) can be measured in serum or urine for 1 to 3 days, but perhaps more importantly, these two markers also can be found in hair for extended periods (Wurst et al., 2004; Pragst & Yegles, 2006). This is because growing hair follicles exchange materials with the blood supply, and markers that are in transit through the blood can become sequestered and deposited in the growing hair shaft. Work by Friedrich Wurst and his collaborators in both Europe and the United States have determined that EtG is an excellent direct marker and can be found in urine for many days after drinking; it also can be found in hair and serum. Varga et al (1998) reported that phosphatidyl ethanol (PEth) is an excellent direct marker for drinking, even in normal drinkers, for up to 14 days. Wurst et al (2004) reported that PEth, found in the red cell fraction of the blood, can be detected for up to 1 week. Aradottir et al., (2006) have shown PEth correlates well with alcohol consumption. Both EtG and PEth are sensitive indicators of recent drinking. METHODS This study conducted between 2004 and current has engaged the cooperation of 537 interlockusing DUI offenders in Alberta, Canada. In exchange for cash payments, study subjects have been invited to sit for interviews, fill in questionnaires and agree to have their blood, urine and/or hair sampled for measurement of alcohol markers. While all study subjects agreed to provide samples as a condition of entry into the subject pool, not all have followed through with the measurements as yet. Data are still coming in, not all samples have yet been analyzed, and some types of specimen were more agreeably provided than others. Accordingly the sample sizes of blood and hair measures are variable. Nonetheless, the question under study is a straightforward examination of the extent to which self-reported information, gleaned from structured interviews or assessments, and alcohol biomarkers from blood, hair or urine can predict intermediate and/or long term indicators of DUI risk. The intermediate indicator of DUI risk is based on breath tests (BAC) data in the ignition interlock log file, and the longer term indicator is the low sensitivity but 100% high specificity problem indicator of future repeat DUI offenses. We have previously demonstrated a strong relationship between the rate of elevated BAC tests in the interlock record and future DUI likelihood (Marques et al., 2001, 2003)
Most of the assessments and alcohol markers were sampled at the time of interlock installation and six months later, often at the time of interlock removal. Since the baseline samples at this time have the largest number of cases, the analyses reported here are restricted to the baseline samples. Self-Report and Interview Assessments The assessment information represents 5 subscales of the Drinker Inventory of Consequence (DRINC), the Alcohol Use Disorders Inventory (AUDIT), both the full instrument and the 3 consumption items, the 5 subscales of the Temptation Restraint Inventory (TRI) and the 30 day prior quantity and frequency of drinking reported via the Timeline Followback (TLFB). The DSM4 alcohol dependence and alcohol abuse diagnostic is available from the Computerized Diagnostic Interview Schedule (DIS-C), but only a partial subset has been scored so far. Transportation (vehicle use) Surveys have been collected but are not yet analyzed. Most instruments were administered Pre and Post, but only the Pre assessments are considered here. Biomarkers The routine markers ALT, AST, GGT and MCV were measured by Dynacare Kasper Medical Laboratories in Edmonton, Alberta Canada where the samples were collected. Heparinized whole blood for PEth was collected by Dynacare for shipment to Lund Sweden, in two batches where analysis was performed at the Dept Neurochemistry by Dr. Aradottir. Similarly, serum has been collected for measurement of %CDT (via the Axis-Shield kit) at the University of Texas at San Antonio to the laboratory or Dr. Javors. Hair samples were collected by project staff and have been shipped and analyzed in two separate shipments to Berlin Germany for FAEE measurement in the laboratory or Dr. Pragst, reserve samples were sent from Germany to Luxembourg for the measurement of EtG in the hair in the laboratory of Dr. Yegles. Urine samples were later collected for measurement of EtG and EtS in urine and these samples will be sent to Austria to the laboratory of Dr. Frieder Wurst. Additional samples of all specimens are ready for shipment once arrangements can be completed. All markers were evaluated as both raw data and statistically transformed to a more normal distribution of values in order to estimate predictive utility. Outcomes The intermediate outcome is the record of BAC tests found in the interlock record. These breath tests are strong proxies for future impaired driving risk as we have previously shown. Long term recidivism outcomes will require more time. At present, among 398 of our offender sample with recidivism information, only 9 have re-offended. Accordingly it is premature to attempt to estimate prediction of future impaired driving especially as post-interlock exposure time varies among the group.
RESULTS The sample sizes of baseline variables available at this time are shown in Table 1. Variable
N=
Data
Driver Records
Alcohol arrests
398
9, or 2.3% new alcohol arrests
Driver Records
Moving Violations
398
124, or 31% moving violations
Interlock Data Log
High BAC tests
277
171, or 66% with 1 test ≥.02 g/dL
ALT, AST, GGT, MCV
292
PEth, %CDT
139
FAEE in hair
92
EtG in hair
35
EtG/EtS in urine
0
Timeline Followback (TLFB)
448
Other Self-Report (AUDIT, DRINC, TRI)
230
General Demographics
424
The criterion variable discussed here is the proportion of interlock BAC tests for each driver that equal or exceed .02 g/dL. In Alberta, the lockout point is .04 g/dL, but at this early stage in the analyses the .02 g/dL criterion is a more sensitive measure. For either criterion, the results will be similar as the correlation between .02+g/dL and .04+ g/dL criteria is r= .740 (P=.000, N=277). However, the .02 criterion draws in 32% more of the sample (increasing sensitivity at the cost of specificity). Of the 277 offenders with interlock log file data, 169 also have data on ALT, AST, GGT and MCV; fewer still have both BAC and data for the other biomarkers. With a relatively small sample size and skewed distribution of results (most marker values cluster around the low end) extreme values can have a large influence. To control for this we have calculated and used normalizing transformations for all skewed variables, in some analyses both the transformed and the raw data are described.
Self-report or Biomarkers or Both? A quick way to characterize the relative contribution of self-report measures and biomarkers as predictors of interlock BAC test data is to extract factor scores. In this screening method we found that both a general self-report factor (33% of the variance) and a general biomarker factor (35% of the variance) entered the stepwise regression equations for predicting start up BAC tests ≥.02 g/dL. Accordingly, each method contributes unique predictive information. The tables that follow characterize the relationships between the assessments, the biomarkers, and the interlock BAC tests. Biomarkers and Self-Report Assessments Eight markers were evaluated against the self-report and interview assessments, six are shown in the chart below (ALT is similar to AST but weaker), MCV is a well-distributed and very normal marker, but shows only a weak significant relationship to one assessment. The marker most strongly correlated with assessments was PEth. All the DRINC subscales (Physical, Interpersonal, Intrapersonal, Social Responsibility, Impulse Control), and two of the Temptation Restraint Inventory subscales (Emotion, Governance) were correlated P.02 startup
BAC >.04 startup
BAC >.02 startup normalized BAC >.04 startup normalized
Pearson Correlation Sig. (2-tailed) N Pearson Correlation Sig. (2-tailed) N Pearson Correlation Sig. (2-tailed) N Pearson Correlation Sig. (2-tailed) N Pearson Correlation Sig. (2-tailed) N
PETH -.119 .180 129 .245** .006 126 .331** .000 126 .219* .014 126 .255** .004 126
GGT -.008 .906 229 .329** .000 170 .306** .000 170 .269** .000 170 .230** .003 170
EtG hair -.061 .742 32 .427* .019 30 .347 .060 30 .422* .020 30 .449* .013 30
FAEE hair .003 .978 81 .158 .190 70 .330** .005 70 .137 .259 70 .239* .046 70
AST .012 .858 229 .337** .000 170 .289** .000 170 .222** .004 170 .158* .040 170
%CDT -.035 .692 129 -.004 .962 126 .046 .612 126 -.057 .526 126 -.005 .953 126
**. Correlation is significant at the 0.01 level (2-tailed). *. Correlation is significant at the 0.05 level (2-tailed).
It is evident from Table 3 that PEth and GGT sampled at the time the interlock was installed (with 126 and 170 subjects respectively) are significantly predictive of later elevated BAC tests collected in the approximately 6 month period after installation. Also, it is noteworthy that none of the alcohol markers is at all correlated with non-alcohol high risk driving in general (moving violations). While the sample sizes for the hair measures (EtG and FAEE) are very small, the relationships are quite strong between these long-term alcohol exposure measures from hair and the long-term BAC test patterns found in the interlock record. It should be noted that at the current stage of development of this research we are using marker results as continuous variables. Before these findings can be clinically/practically relevant to road authorities or treatment providers we will need to report on cutoff levels of blood or hair to define high risk groups. Report Assessments and Interlock BAC Tests Some of the self-report assessments are nicely associated with higher rates of interlock BAC tests, but the magnitude of the correlation coefficients in Table 4 that combines self-report measures with BAC tests, show these measures are less promising than the blood and hair measures for predicting the interlock BAC tests elevated above .02 g/dL or .04 g/dl (.04g/dL is the actual failed test criterion in Alberta). The most promising looking of the self-report measures are from Timeline Followback (TLFB) represented by the first 6 row items, and from the DRINC, represented here to save space as the total of all subscales. The AUDIT (nor AUDIT_C) and the DSM dependence measures were not predictive of elevated interlock tests. Future Path Model The research plan from the outset was to acquire different sets of potential predictors from both self-report and various biomarkers to initially predict interlock BAC tests and subsequently to use those interlock BAC tests along with the assessments and markers to predict future recidivism. Currently there is too much variability in sample sizes to evaluate a structural equation, path model without resorting to the systematic guesswork of imputation. Repeat
offenses continue to accumulate, and soon there will be more blood and hair measurements if funds and laboratories continue to allow for it. TABLE 4: Pearson correlations of Interlock BAC tests and Self-Report Assessments Correlations
Max Drinks on One Day
Total Drinks Consumed
Longest Abstinence Period
Longest Drinking Period
Percent of all days that drinking occurred Average Drinks per Week AUDIT Total
AUDIT_C
DRINC Total
DSM4 alcohol dependence
Pearson Correlation Sig. (2-tailed) N Pearson Correlation Sig. (2-tailed) N Pearson Correlation Sig. (2-tailed) N
non-alcohol moving violation (pts or jail) AFTER intake .097 .066 360 -.006 .917 360 .055 .298
Pearson Correlation Sig. (2-tailed) N Pearson Correlation Sig. (2-tailed) N Pearson Correlation Sig. (2-tailed) N Pearson Correlation Sig. (2-tailed) N Pearson Correlation Sig. (2-tailed) N Pearson Correlation Sig. (2-tailed) N Pearson Correlation Sig. (2-tailed) N
360 .008 .879 360 .009 .859 360 -.006 .913 360 -.004 .956 212 -.069 .321 212 .046 .514 200 .042 .526 227
BAC >.02 startup .112 .080 244 .196** .002 244 -.186** .004
BAC > .04 startup .054 .400 244 .165** .010 244 -.133* .038
BAC > .02 startup normalized .189** .003 244 .156* .015 244 -.181** .005
BAC > .04 startup normalized .099 .123 244 .164* .010 244 -.145* .023
244
244
244
244
.218** .001 244 .231** .000 244 .197** .002 244 .086 .224 200 .121 .088 200 .241** .001 191 .108 .117 213
.205** .001 244 .194** .002 244 .165** .010 244 .055 .438 200 .073 .303 200 .173* .017 191 .129 .060 213
.074 .252 244 .178** .005 244 .156* .015 244 .126 .076 200 .170* .016 200 .245** .001 191 .135* .050 213
.156* .015 244 .197** .002 244 .164* .010 244 .095 .183 200 .102 .152 200 .224** .002 191 .128 .061 213
**. Correlation is significant at the 0.01 level (2-tailed). *. Correlation is significant at the 0.05 level (2-tailed).
DISCUSSION Interlock BAC tests results are an important predictor of driver risk, but not all drivers cooperate with interlock programs and alternative objective tools are needed to scale risk. It appears that biomarkers are at least as useful, and probably more useful, than self-report or similar verbal assessments especially as we are now beginning to demonstrate this in a cooperative sample of offenders willing to disclose drinking and drinking problems without fear of retribution. A comparable degree of potentially incriminating self-disclosure should not be expected outside of independent research studies like this one.
There was no intervention in this study, other than the interlock device that all subjects were using. It is therefore interesting to note that samples collected at the time of installation were predictive of the likelihood of testing positive for elevated BAC for, on average 6-12 months after the samples were collected. PEth and GGT appear to be particularly good predictors of interlock BAC tests based on these data. Evaluation of direct markers in hair, FAEE and EtG, were interesting but unfortunately too few cases available upon which to draw conclusions at this time. % CDT was the only marker to show a correlation with DSM4 diagnosis of dependence but it did not show much relationship to the other markers or the integrated elevated BAC test measures from the interlock. It may not be surprising that the direct consumption markers were more associated with the interlock BAC tests than was CDT. Finally it should be noted that the use of parametric correlation (Pearson) was practical through use of normalizing transformations of the many skewed marker variables. Further work will evaluate the cutoff criteria that would be necessary for licensing authorities to make practical use of this information. ACKNOWLEDGEMENT This work supported by research grant 5R01 AA014206 from NIAAA. The authors also wish to thank the Alberta Transportation Safety Board and Alcohol Countermeasures Systems Corporation for their supportive cooperation. REFERENCES Appenzeller, B.M.R, Schneider, S., Maul, A., Wennig, R. (2005). Relationship between blood alcohol concentration and carbohydrate deficient transferrin among drivers. Drug and Alcohol Dependence. 79, 261-265. Aradottir, S, Asanovska, G., Gjerss, S., Hansson, P., & Alling, C. (2006). Phosphatidylethanol (PEth) concentrations in blood are correlated to reported alcohol intake in alcohol-dependent patients. Alcohol and Alcoholism, 41(4), 431-437. Bjerre, B., (2005). Primary and secondary prevention of drink-driving by the use of alcolock device and program: Swedish experience. Accident Analysis and Behavior. 37, 1145-1152. Bjerre, B., Marques, P., Selen, J. & Thorsson, U. (2007). A Swedish alcohol ignition interlock programme for drink-drivers: effects on hospital care utilization and sick leave. Addiction. 102, 560-570. Collins, R.L. & Lapp, W.M. (1992). The Temptation and Restraint Inventory for measuring drinking restraint. British Journal of Addiction, 87, 625-633. Marques, P. R., Voas, R. B., & Tippetts, A. S. (2003). Behavioral measures of drinking: Patterns in the interlock record. Addiction, 98 (Suppl. 2), 13-19. Marques, P. R., Tippetts, A. S., & Voas, R. B. (2003). Comparative and joint prediction of DUI recidivism from alcohol ignition interlock and driver records. Journal of Studies on Alcohol, 64(1), 83-92. Marques, P. R., Tippetts, A. S., Voas, R. B., & Beirness, D. J. (2001). Predicting repeat DUI offenses with the alcohol interlock recorder. Accident Analysis and Prevention, 33(5), 609–619.
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