Fail an alcohol test and you could lose your job. But confidence is draining from the blood and urine tests that are supposed to show conclusively whether someone has been drinking 鈥� and the US government has decided it鈥檚 time to take another look at them.
Typically, the body destroys alcohol within 6聽hours, so the tests are designed to pick up tiny amounts of substances such as ethyl glucuronide (EtG) and ethyl sulphate (EtS) that are formed exclusively from the breakdown of alcohol. These remain detectable in urine for almost a week.
But the tests can return a positive result in people who haven鈥檛 drunk any alcohol but have been exposed to minute quantities of it in alcohol-based hand-wipes and mouthwashes, alcohol-free wine, and even foods such as bananas and sauerkraut.
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In the US, several legal cases are under way in which doctors, nurses and other professionals who were being monitored for abstinence but tested positive are protesting their innocence.
Inappropriate action
The US health department鈥檚 Substance Abuse and Mental Health Services Administration (SAMHSA) is already aware of the problem. In 2006 it which declared as 鈥渋nappropriate鈥� and 鈥渟cientifically unsupportable鈥� any legal or disciplinary action based solely on an EtG or EtS test. But at a meeting convened by SAMHSA last month to review the latest scientific and legal evidence, lawyers asked for clearer, quantitative advice to distinguish accidental from deliberate consumption.
鈥淭he courts need guidance from SAMHSA,鈥� says William Meyer, a senior fellow of the National Association of Drug Court Professionals. 鈥淐an SAMHSA set a cut-off level which will reliably predict knowing alcohol consumption, and exclude accidental exposure?鈥� he asked.
The sauerkraut factor
At present, there are no official cut-off figures for lawyers to refer to. A widely used unofficial figure for both EtG and EtS is 0.1聽milligrams per litre of urine 鈥� but recent research in Norway has shown that drinkers of non-alcoholic wine exceed this level for EtS (). Likewise, research in Germany has shown that eating bananas or sauerkraut can push EtG beyond the cut-off ().
Greg Skipper, medical director of the Alabama Physician Health Program, runs a advising people who think they have been unfairly incriminated by the tests. He doubts whether a definitive cut-off can be found, because the overlap between innocent and deliberate exposure is too large to give legal certainty.
He says that there is hope, however, from more recent research on blood tests for another alcohol breakdown product called phosphatidyl ethanol, or PEth. It鈥檚 formed when alcohol combines with fatty lipids on red blood cell membranes, and stays there for the whole month-long life of the cell.
Skipper says that levels of PEth above 20聽nanograms per millilitre of blood are pretty conclusive proof that someone has drunk at least seven standard drinks over a week, a level impossible from accidental exposure. 鈥淧Eth needs more research, but it looks like it will be an excellent direct marker that will indicate significant drinking,鈥� he says.
