WADA figures show reduction in positive doping tests in 2014

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Suspicious drugs were found in more than 3,800 samples out of 283,304 tests carried out worldwide last year, World Anti-Doping Agency figures have revealed.

However, despite an increase in the number of tests carried out, this figure represented a fall from the 2.21 per cent of adverse or atypical findings returned in 2013, when 5,962 such samples were returned from a total of 269,878.

A sample that tests positive for a banned substance does not necessarily mean an athlete has been doping. Some substances can be produced naturally by the body.

Despite the decline, in an interview with BBC Athletics Wada has claimed more than 10 per cent of elite athletes could still be using performance-enhancing drugs.

The International Association of Athletics Federations (IAAF), carried out more than 1,400 tests on an estimated 600-700 athletes in China in 2014. Just two Kenyan runners (Joyce Zakary and Koki Manunga) failed the tests, although the IAAF said samples would be frozen and stored for future reanalysis.

As well as a significant reduction in samples containing adverse findings, in 2014 the number of tests requiring further investigation also fell. Wada credits the introduction of the athlete biological passport for the decline.

Hamish Coffey, head of testing for UK Anti-Doping, told the BBC: "Our aim in the UK is not to be focused primarily on the numbers but more about the quality, which is where our intelligence-led operations come in.

"The reality is there will always be athletes who are determined to cheat and looking at ways of evolving their techniques, which leads to challenges for us.

"It is important we match that and continue trying to evolve our techniques to keep up with them."