* Athletes can be approached for testing anytime, anywhere
* Up to 6,250 samples to be tested at 24-hour lab
* Doping cheats are banned from the Games
By Kate Kelland
LONDON, July 28 (Reuters) - Scientists working around the clock at a specially equipped anti-doping lab on the outskirts of London will analyse more than 6,000 urine and blood samples during the 2012 Olympics.
The process - from obtaining the sample through to delivering what may be career-ending results back to athlete and coach - is highly sensitive and demands high levels of speed, skill and security.
Any of the more than 10,000 athletes can be required to test anytime, anywhere - trackside, poolside, in the athletes village or in private houses and whether they are already in Britain or still at training camps outside of the country.
The testing experience - which has the potential to bring shame and humiliation down on anyone caught cheating - starts when an Olympic anti-doping official approaches an athlete and tells them they've been selected.
It's a conversation that will take place with thousands of athletes across all sports and nationalities and will include all medal winners, organisers say.
Many top athletes will face repeat tests before the Games end on August 12.
If they refuse to give a sample, athletes can be banned from coming to London to compete or they can be sent home, as Hungarian discus thrower Zoltan Kovago found out last week.
Those who agree to be tested are accompanied by a chaperone at all times until they get to a doping control station where samples are taken.
The athlete provides a sample - of either urine or blood -which is then split into two lots, A and B, so that one can be used for back-up testing if results on the A sample are queried.
The athletes themselves are required to seal the bottles and fill in the paperwork - a protocol designed to minimise the risk of contamination.
The sample bottles have tamper-proof seals that can only be opened using specialist equipment in the lab.
In a detailed statement on Saturday about how the Albanian weightlifter Hysen Pulaku was caught, the International Olympic Committee (IOC) said that after traces of the anabolic steroid stanozolol were found in his A sample, given on July 23, he was contacted and told of the findings.
Pulaku became the first athlete to be ejected from London 2012 and now faces a possible two-year sanction by the International Weightlifting Federation.
Both Pulaku and his coach and uncle Sami Pulaku said they could not understand how the drug ended up in the athlete's body, but they accepted the result and said they would not be contesting the decision.
The coach, who according to minutes of the meeting said he was "depressed" to hear Hysen Pulaku had tested positive, also said he didn't feel it was necessary to test the B sample.
But the weightlifter disagreed, and asked for tests on the B sample to be carried out. Under a strict protocol, designed to ensure fairness, Pulaku's B sample was opened and analysed in his presence on July 25.
The results, which confirmed the A sample findings, were sent to the IOC the following day.
ANONYMITY ENSURES SECURITY
Experts say one of the most important features of accurate and secure drug testing is anonymity.
"Being found guilty of being a dope cheat in sport carries an enormous stigma, so it is only fair to the athletes that systems for testing are flawless," said Leon Edwards who runs Versapak Doping Control, a tamper-proof equipment maker.
"Modern procedures have every step covered, from incorruptible sample-gathering, tamper-evident methods of transportation and robust lab tests," he added.
At London 2012, samples are identified only by a barcode from the point at which they are secured in bottles. This means neither the couriers carrying the samples to and from the lab, nor any of the scientists carrying out the tests, are able to know which athlete is being tested.
The samples are sent on an hourly basis and arrive at the anti-doping lab in Harlow, east of London, in a blue silver-lined box and have the barcode scanned in before testing begins.
The first task is for one of the 150 international scientists working to open and analyse sample A, and freeze and securely store sample B. The testing uses liquid chromatography and mass spectrometry equipment that can screen for more than 240 banned substances in less than 24 hours.
David Cowan, head of the Drug Control Centre at King's College London and the man overseeing London 2012's anti-doping regime, has said his team can screen up to 400 samples a day and expects to analyse around 6,250 in total during the Games.
"It is always a sad day when a cheating athlete is caught," IOC spokesman Mark Adams said on Saturday. "I hope there will not be more." (Editing by Jason Neely)
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