Indirect Markers

A number of indirect biological markers are used to detect alcohol consumption, namely: 

Serum GGT, a liver enzyme, is the most useful of the currently available tests but has only moderate sensitivity and specificity. It is elevated in 30% of patients with alcohol dependence in primary care and, depending on the clinical circumstances, 50 to 70% of hospitalised patients with alcohol dependence. However, it is less likely to be raised in women and young people. It is part of the multichannel biochemical analysis offered under the Medicare Pathology Schedule, as is AST and ALT.  

Elevated GGT levels are not specific for alcohol use and may occur with other conditions, including: 

• • • obesity (now the most common cause for elevated GGT levels in some populations) 

    • obstructive liver disease 

    • medications that induce hepatic cytochromes (such as anticonvulsants). 

CDT is a sensitive and highly specific marker of unhealthy alcohol use, there being very few causes of an elevated CDT other than alcohol. However, the CDT assay is not reimbursed by Medicare and is rarely used outside forensic and medicolegal settings.  

Recently discovered biomarkers such as 5-HTOL, PEth, FAEE and EtG are relatively unaffected by disease state, but their cost and exclusion from the Medicare schedule limits their usefulness in everyday clinical practice.

Because of the greater sensitivity and specificity of questionnaire approaches (such as AUDIT) these are preferred to biological markers. Biological markers should only be used as an adjunct to other screening measures.