Scientists have found a way to detect use of a banned performance-enhancing drug by athletes for the first time.
Doping technology is moving rapidly
Sports cheats use the protein synacthen to stimulate the body to increase production of corticosteroid hormones, which help them to train harder.
Unlike direct injections of the hormones, this has proved impossible to detect until now.
The breakthrough, by the German Sport University Cologne, appears in Rapid Communications in Mass Spectrometry.
The use of corticosteroids is banned as, apart from giving users an unfair advantage, they are associated with a raised risk of a wide range of health problems, including cancer, heart attacks, impotence and mood swings.
The new test enables the detection of synacthen even though it is found in the blood only at very low concentrations - around 10 million times less than other proteins in blood plasma.
Called immunological purification, it works by specifically searching for minute traces of the protein.
To confirm that the immunological purification has pulled out synacthen, the protein is then subjected to a further two-stage test.
This combination of chromatography separation and mass spectrometric analysis allows scientists to produce a chemical fingerprint of the molecule - a fingerprint that uniquely identifies it.
Lead researcher Dr Mario Thevis said: "If the drug-testing authorities adopt this new test, it will close a gap in the current drug-testing system, and mean that athletes will no longer be able to get away with this form of cheating."
Dr John Brewer, director of the Lucozade Sports Science Academy, said: "If this is a viable and accurate test then hopefully once athletes know about it they will see sense and steer well clear of using synacthen in the future.
"Everybody involved in trying to eradicate illegal drugs from sport will welcome this advance. We very much want the drug testers to stay one step ahead of the drug users."
However, Dr Brewer said the pace of technology was so fast that the authorities faced a constant battle to outwit their opponents.
Andy Parkinson, head of drug-free sport operations at UK Sport, said any step forward in the detection of previously undetectable substances was welcome.
"The World Anti-Doping Agency is continually looking at ways in which to have more effective analysis and this technique could be a useful addition to our anti-doping armoury."