A test for anabolic steroids that could help to crack down on drug cheats in sport has been developed by researchers in Germany and Canada.

Banned steroids such as nandrolone continue to be used by athletes to boost their muscle mass, and analysing urine samples for 19-norandrosterone, a metabolite of nandrolone, can uncover evidence of abuse. But traces of this chemical are also made naturally in the body, and current tests cannot determine whether the norandrosterone has a synthetic or physiological origin.

Moritz Hebestreit and colleagues from the German Sport University Cologne, in collaboration with a researcher from the Montréal Anti-doping Laboratory at the Institut Armand-Frappier-Santé, have now developed a technique that can distinguish between the two. This could help to resolve cases where athletes have elevated levels of 19-norandrosterone in their urine but insist that they have never taken steroids.

Hebestreit's test differentiates between synthetic and natural norandrosterone by analysing the ratio of ¹³C to ¹²C isotopes in urine samples using a technique called gas chromatography combustion isotope mass spectrometry. The synthetically produced compound has a lower concentration of the ¹³C isotope because it is produced from a plant source with intrinsically less ¹³C than that from normal dietary sources. The test is able to detect concentrations of 19-norandrosterone as low as 2 ng per ml of urine - the level currently allowed by the World Anti-Doping Agency.

Tony Moffat, Head of the Centre for Pharmaceutical Analysis at the University of London, UK, said that the 'excellent' method was suitable for use in anti-doping programmes.

Hebestreit hopes to extend the technique to discover the origins of other drugs by studying different isotope ratios, such as D to H and ¹⁵N to ¹⁴N.

Nicola Burton