BLOOD ALCOHOL CONCENTRATION OR GAMMAGLUTAMYL TRANSPEPTIDASE AS A PREDICTOR OF PROBLEM DRINKING

AMONG DRUNK DRIVERS?

*J. A. Dunbar, M.B., Ch.B., M.R.C.C.P, D.M.J. ;M. S. Devgun, Ph.D., MIBiol.; J. Hagart, MSc.;

S. A. Ogston, M.A., MSc.; and B. T. Martin, BSc., Ph.D.

SYNOPSISProblem drinkers among drunk drivers were identified by

the estimation of gammaglutamyl transpeptidase at arrest. The prevalence of problem drinking among drunk drivers is discussed. Results of a follow-up study showing deterioration in alcohol problems following revocation of the driving license are shown. Implications for changes in the United Kingdom drinking and driving laws are discussed.

INTRODUCTIONSince May this year the Road Traffic Act in the United

Kingdom has been amended to recognize "high-risk offenders" among drunk drivers. By this act high risk offenders are defined as drivers who are convicted of drinking and driving on 2 occasions within 10 years with blood alcohol concentrations above 200 mg/100 ml (43.4 mmol/1) or refusals to provide a specimen. Upon arrest the driver must be investigated by the Medical Advisers of the Department of Transportation for evidence of dependence on alcohol or a drink problem before his driving license is restored.

An alternate method of identification may include estimation of gammaglutamyl transpeptidase (GGTP) at arrest (Dungar et al., 1982; Dunbar et al., 1983; Pikkarainen & Pentilla, 1980) . This enzyme is induced by alcohol and generally accepted as a reasonably sensitive indicator of excessive alcohol consumption. In this study we compared the advantages of GGTP over blood alcohol concentration (BAC) and compared the GGTP analyses with information retrieved from the drivers' medical records (Wilkins, 1974).

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Department of Community & Occupational Medicine, & Biochemical Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee DDI 9SY, Scotland,UNITED KINGDOM.

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SUBJECTS AND METHODS

To stimulate the "Saturday night drinking driver" we invited 54 healthy drivers (53 men and 1 woman), aged 18 to 51 years (mean 33.3 years), to drink wine, spirits, and beer freely over 5 hours. Before drinking a baseline blood sample was taken; a 2nd sample was taken l h hours after theend of the drinking session and a third 8 hours after thesession. Gammaglutamyl transpeptidase activity was measured in all 3 samples and blood alcohol concentration in the 2nd and 3rd samples.Experiment II

Motorists who were arrested for drinking and driving in Tayside Region were invited to participate in Tayside Safe Driving Project; 96% of the drivers agreed to participate representing 51% of the drivers arrested in the Region. Ofthese, 96.6% of the drivers were male. The mean age was32.5 years, with a range from 17 to 70 years. At the time of arrest 5 ml of blood were taken and divided into 3 samples: one was given to the driver, the second wasanalyzed for blood alcohol concentration by the public analyst, and the third was used to measure the serum activity of GGTP using a centrifugal fast analyzer (37°C). An examination of medical records to detect drugs or diseases known to raise GGTP activity was carried out but none was detected.

A 2-page structured questionnaire was sent to the general practitioners of drivers who lived within Tayside. The results of this study are presented in another paper at this meeting. Returned questionnaires were given an alcohol rating score from "1" to "3." ("1" = alcohol problemsstated to be present by general practitioners; "2" = 2 or more covert indicators of problem drinking in their medical record, e.g., gastritis, morning shakes, or marital difficulties; "3" = "clean" medical record with fewer than 2 covert indicators or illnesses/injury unassociated with alcohol.)Experiment III

A sub-group of 128 subjects, chosen for geographic proximity, gave a second blood sample 5-9 months after arrets. Gammaglutamyl transpeptidase activity was measured again. (We found no statistically significant difference between this sub-group and the overall population of drunk drivers.)

Experiment I

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RESULTS

Of the sample of 54 drivers, 45 had peak blood alcohol concentrations above the legal limit for driving (80 mg per 100 ml; 17.4 mmol/1) 1% hours after the drinking session, corresponding to an alcohol ingestion of greater than 100 g and, of these, 14 were still above the legal limit 8 hours after drinking. In these cases alcohol ingestion was greater than 300 g. No significant differences in GGTP activities were observed in 9 subjects with abnormal values (greater than 50 iu per liter). By 2-way analysis ofvariance we found significant variation between the times of testing, which indicated a difference in the mean GGTP activities on the 3 occasions, the main activities being 37. 3, 34. 9, and 36.5 iu per liter, respectively (S.E. ofdifference between 2 means = 0.54). The mean at 1h hours was about 5% lower than at base line and at 8 hours after ingestion (£ = less than 0.01). This was fairly smallcompared with a typical inter-individual variation which is of the order of + 30 units. Biochemically these differences were not important and may have been a reflection of hemodilution by alcohol; no differences were, however, observed with subjects consuming different amounts of alcohol. Neither overall mean GGTP activities nor variation in values over time depended on the amount of alcoholingested (Table 1) .

Table 1

Amount of Alcohol Ingested, Blood Alcohol Concentration and Gammaglutamyl Transpeptidase Activity (Mean Values Expressed + SD)

Experiment I

Alcoholingested(g) No of

Subjects

Mean blood alcohol mg/100 ml)*

Mean -glutamyltranspeptidase(IU/1)

After 6% hours

After 13 hours At start

After 6h hours

After 13 hours

Nil 1 0 0 19 21 2051-100 4 46 + 49 10 + 21 35 + 21 31 + 18 35 + 21

101-150 6 111 + 66 25 + 45 50 + 57 48 + 57 48 + 53151-200 12 140 + 32 14 + 15 25 + 9 22 + 9 24 + 10201-150 9 162 + 72 43 + 47 39 + 27 36 + 27 40 + 29152-300 10 195 + 60 56 + 43 39 + 42 37 + 41 37 + 38301-400 10 238 + 40 108 + 58 39 + 29 37 + 30 38 + 28401-500 2 275 + 4 115 + 13 59 + 35 57 + 42 58 + 35

* 1 mg/100 ml = 0.217 mmol/1.

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Experiment IIOf all the drivers arrested, incorporated in the first

phase of the study, 24% had raised GGTP activity (Figure 1). Drivers with abnormal enzyme activity had blood alcohol concentrations throughout the entire range, including concentrations that were under the legal limit for driving. The correlation between blood alcohol concentration and enzyme activity at the time of arrest was highly significant, although the degree of association was only moderate (r = 0.22; £ less than 0.0001).Experiment III

A comparison of serum GGTP activity at the time of arrest with that 5-9 months later, in those who co-operated in the follow-up study, showed a significant association (r = 0.88; £ less than 0.0001; Figure 2). In 3 subjects enzyme activity was high at arrest but in the reference range 5-9 months later; in 5 subjects enzyme activity was in the reference range at the time of arrest but was raised 5-9 months later; in 23 subjects (18%) enzyme activity was high at the time of arrest and continued to be high at follow-up. Of the subjects recalled for follow-up with blood alcohol concentrations over 17.6 mmol/1 (80 mg/100 ml), 25 (22%) had raised GGTP activity at the time of arrest; of these 88% were unchanged at follow-up (Figure 3) . Thirteen (45%) ofthe recalled subjects with blood alcohol concentrations over43.6 mmol/1 (200 mg/100 ml), the UK suggested index ofproblem drinking, had raised enzyme activity at the time ofarrest and 10 of these had raised activity at follow-up.

General practitioners completed and returned 93% of the questionnaires distributed. Twenty-two (13%) had an alcohol rating of "1"; that is, the general practitioners were aware of the patient's alcohol problems. A further 42 drivers(24%) had 2 or more covert indicators of problem drinking in their medical records. Alcohol rating and gammaglutamyl transpeptidase activity were significantly related but not blood alcohol concentrations and alcohol rating (Table 2).

DISCUSSIONSerum GGTP activity is generally considered to be a

reasonably sensitive indicator of problem drinking (Whitehead et al., 1978); thus, our results indicate that most high risk offenders have blood alcohol concentrations in the range 17.6 - 43.2 mmol/1 (80-199 mg%). However, the problem drinkers may also be found among drivers with alcohol concentrations below the legal limit. Our results indicate that any attempt to identify high risk individuals

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based on blood alcohol concentrations would be an arbitrary choice, likely to miss a large proportion of high risk offenders.

Table 2

Number of Drivers with an Alcohol Problem Rating of 1, 2, or 3 Against Blood Concentrations of Alcohol and Against

-glytamyltranspeptidase Activity at Time of Arrest

Alcohol problem rating

1 2 3 Total

No (%) No (%) No (%) No (%)

Blood alcohol concentrations (mg/100 ml)*

< 80 4(18) 10(24) 26(24) 40(23)81-105 7(32) 16(38) 41(37) 64(37)

151-200 7(32) 9(21) 22(20) 38(22)> 200 4(18) 7(17) 21(19) 32(18)

TOTAL 22(13) 42(24) 110(63) 174(100)

-glytamyltranspeptidase activity (IU/1)

< 50 13(59) 33(79) 95(36) 141(81)> 50 9(41) 9(21) 15(14) 33(19)

TOTAL 22(13) 42(24) 110(63) 174(100)

Chi-squared = 1.70, df = 6, |> = greater than 0.0.

Chi-squared = 9.09, df = 2, £ = less than 0.025.

Conversion: Traditional units to SI - Blood alcohol: 1 mg/lOOml 0.22 mmoi/1.

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Theoretical objections to GGTP have been largely eliminated by this study: there is no binge effect raisingthe enzyme over a short time course, and the prevalence of diseases and drugs amongst drunk drivers is so low that the problem of false positive does not occur. Indeed, in the larger Tayside Safe Driving Project study of 1047 drivers no cases of raised enzyme could be attributed to disease or drugs. In two further studies, the results of which are being presented at this meeting, it was shown that GGTP accurately reflects the spectrum of social and medical facets of problem drinking.

Serum gammaglutamyl transpeptidase activity has an additional advantage over blood alcohol concentration. When measured more than 5 months after arrest it indicates whether or not the driver is controlling his drinking. Although it seems that conviction results in a restoration of normal activity, this occurs in very few drivers: inless than 10% of our subjects. It is far commoner to find continuing abnormal activity or increasing abnormality, indicating that conviction has not moderated the driver's alcohol consumption. Where there is sustained abnormal or rising enzyme activity, but no other known cause of disturbed liver function, it seems unwise to restore the driver's license.

A quarter of convicted drivers in this study had raised serum GGTP activity. Given the reported sensitivity, specificity, and predicted value of the test, a third of drivers in the study may well be problem drinkers (Baxter et al., 1980).

CONCLUSIONSAmong drunk drivers serum GGTP activity measured at the

time of arrest is a better indicator of problem drinking than blood alcohol concentration.

ACKNOWLEDGMENTThis study was funded by grants from the Biomedical

Committee, Scottish Home and Health Department and the Association of Police Surgeons of Great Britain. We thank Chief Inspectors Ritchie, Nairn and Palmer; Dr. D. C. Marshall and the Police Surgeons; Professor Knox and the general practitioners of Tayside; Professors Griffith and Mair, Mrs. Bree, Brown, Kynoch, Montgomery and Reid, all of whom helped collect data for this study. Correspondence to Dr. J. A. Dunbar, 325 Strathmartine Road, Dundee DD3 8NE.

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REFERENCESBaxter, S., Fink, R., Leader, A. R., and Rosalki, S. B.

(1980). Laboratory Tests for Excessive Alcohol Consumption Evaluated in General Practice. British Journal on Alcohol and Alcoholism, 15: 164-66.

Dunbar, J. A., Hagart, J. , Martin, G. E., et al.(1982). Drivers, binge drinking and gammaglutamyltranspeptidase. British Medical Journal, 285: 1083.

Dunbar, J. A., Martin, B. T. , Devgun, M. E. , et al.(1983) . Problem drinking among drunk drivers. British Medical Journal, 286: 1319-1322.

Pikkarainen, J. , and Pentilla, A. (1980). Screening of arrested drunk drivers for alcoholism. In Goldberg, L. (ed.), Alcohol, Drugs, and Traffic Safety. Stockholm: Almgvist & Wiksel International.

Wilkins, R. (1974) . The Hidden Alcoholic in General Practice. London: Paul Elek Scientific Books.

Whitehead, T. P., Clark, C. A., and Whitfield, A. G. W. (1978). Biochemical and haematological markers of alcoholintake. Lancet, 1: 978-781.

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