The "biological passport" method, which has been employed by cycling and athletics, takes various samples of a competitors biological data and looks for abnormalities in normal biological levels in order to spot doping, as opposed to testing for individual substances.

US Open champion Andy Murray is one of a number of top players that have called for stricter anti-doping measures in tennis, and it looks as though the International Tennis Federation (ITF) is listening.

"We're looking very, very closely at it ["biological passport" method] and I think there's a reasonably good chance that will be operational probably towards the end of 2013," said Dr Stuart Miller, head of the ITF science and technical department.

Figures show that the ITF conducted just 21 blood tests out-of-competition in 2011, a figure that must be improved, according to Miller.

"We think we need to increase the proportion of blood testing we do under the programme and we think we could also do with tending to increase the proportion of tests we do out of competition," he said.

US Open champion and London 2012 Olympic gold medallist Andy Murray has backed the possible introduction of the "biological passport" system

Murray recently backed the suggestions of employing the "biological passport" method at an Australian Open press conference, saying: "I think it's something that all sports are now trying to improve their doping controls and make it better, you know, make sure that every sport's as clean as possible.

"If that's more blood testing or the biological passports, that's something we need to do and improve in tennis, as well."

World number one Novak Djokovic revealed last week that he had not been asked for a blood sample for some time.

"In the last six, seven months I haven't been subjected to blood tests." he said

"They were much more regular in the past, but they stopped taking them.

"The system we use in tennis is a bit more complex because we have to fill documents in which we communicate every day our transfers but if this serves to keep this sport clean it's welcome.

"Many complained but I think that the more draw blood are made the best is.

"I have nothing against the anti-doping federation testing me 10, 20, 30 times a year."

Disgraced cyclist Lance Armstrong claimed that the introduction of the "biological passport" method to cycling deterred him from doping further

Self-confessed drug-cheat cyclist Lance Armstrong cited the implementation of the "biological passport" method in the sport as one of the main factors that halted the doping regime that he covered-up throughout his career in his interview with Oprah Winfrey, screened last week.

"It's a question of scheduling," he said

"I know that sounds weird, but two things changed this - the shift to out-of-competition testing and the biological passport.

"And it really worked."

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