Clinical and legal aspects of hair testing for alcohol

Commonly used laboratory tests for alcohol use (MCV, GGT, LFTs and CDT) show damage caused to the body by alcohol, but do not indicate whether alcohol was the cause.  Direct tests for alcohol are therefore likely to be helpful. It is possible to measure alcohol levels in the blood and the breath, but these fluctuate with alcohol use and are therefore only useful for indicating very recent consumption of alcohol (within the last few hours).  Metabolites of alcohol (ethyl glucuronide and fatty acid ethyl esters) found in the body indicate that alcohol has probably been consumed.  These metabolites can be found in the urine, allowing another test of recent use, but they are also incorporated into hair.  With hair growing slowly, it is often assumed that the presence of these metabolites in hair indicate that alcohol has been consumed in the period in which the hair was growing. This has formed the basis for hair testing for alcohol in legal settings.  However, interpreting hair test results is complicated; where this has been done with lack of expertise, there have been miscarriages of justice.  This lecture considers the current status of knowledge about hair testing and what can – and what cannot – be inferred from the results of a hair strand test for alcohol.