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A discussion of biomarkers in the detection of alcoholism:
Fred Frick, M.D., Medical Director
ISMA, Physician Assistance Program
Chemical dependency — and alcohol in particular — can commonly be found among patients in primary care practices. Examples over the last 25 years can demonstrate the prevalence of alcoholism in typical outpatient settings, as well as general hospital inpatient populations.
The most important tool in accurate diagnosis of alcoholism remains a high index of suspicion. Yet, the science of bio-markers in alcoholism has advanced a great deal in recent years.
The mean corpuscular volume (MCV) is of low sensitivity and moderate specificity. When you have a non-anemic macrocytosis patient, regard the condition as suggestive of recent heavy alcohol intake. More directed diagnostic efforts should be undertaken.
Gamma glutamyl transferase or GTT is another of the more traditional biomarkers. It is of moderate sensitivity and specificity and when elevated suggests recent heavy alcohol intake.
Of course, a number of false positives can occur, particularly in patients with obesity and diabetes, whereby the patient may have nonalcoholic steatohepatitis or NASH. Many of us were taught that AST and ALT are hepatic markers, but these are even less sensitive and specific. An ALT/AST ratio of 2:1 or greater is particularly suggestive of alcoholic hepatitis.
In monitoring, we have more recently started to use ethyl glucuronide or EtG because this metabolite has high sensitivity but, at this time, unknown specificity. It can detect small amounts of alcohol up to two or three days after ingestion. EtG serves as a common detection tool for monitoring patients in recovery from alcoholism.
However, science has not caught up with practical use of the tests because false positivity is probably higher than initially thought. While a positive EtG does not prove ethyl alcohol ingestion, most authorities agree a negative EtG does definitely prove abstinence.
Laboratories across the country are doing carbohydrate deficient transferring (DCT), an FDA-approved blood test for detecting heavy alcohol consumption. DCT is also used to monitor abstinence and identify relapse in patients with alcohol dependence. Its sensitivity is in the range of 60 to 70 percent with a specificity of 95 percent. In contrast to GGT or AST and ALT, DCT is not affected by common liver conditions other than alcohol-induced liver disease.
For primary care physicians, the best tools remain a high index of suspicion, knowledge of the multiple presentations of alcoholism, and a watchful eye on the MCV and GGT. Make sure you know about referral sources for further testing and evaluation if necessary.
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