Aug. 21, 2008 -- With four days to go before the closing ceremony of the Beijing Olympics, only five athletes have tested positive for doping.
By comparison, 26 athletes were caught cheating at the Athens Games in 2004. And International Olympic Committee President Jacques Rogge had predicted that 30 to 40 athletes would fail doping tests during the 2008 Games.
To the optimists, this year's figure looks like progress.
But to the cynics -- and several anti-doping researchers -- it's an indication that the dishonest athletes may simply be getting better at avoiding detection.
"It definitely does raise flags when only four test positive," Dr. Anthony Butch, director of the UCLA Olympic Analytical Laboratory, told ABCNews.com before news broke that a fifth athlete, the Ukraine's silver heptathlon medalist, was under investigation for a positive doping test.
"Being suspicious as a lab [researcher], you wonder: Are they slipping through the cracks?" Butch said.
His laboratory is a leading research institution in the field of athletic doping and one of few U.S. laboratories accredited by the World Anti-Doping Agency, an independent, international organization charged with coordinating and monitoring anti-doping efforts in professional sport.
Since the Athens Games four years ago, the anti-doping agency and Olympic committee say they have ramped up anti-doping efforts. In 2004, they administered 3,500 doping tests. This year, the IOC said it will analyze 4,500 blood and urine samples to test for banned substances.
Recognizing that available tests may not be advanced enough to keep up with sophisticated doping methods, the committee also announced that it will store all drug testing samples for eight years. Previously, it stored samples that tested positive for 90 days and samples that tested negative for 30 days.
David Howman, director general of the World Anti-Doping Agency, said Rogge's prediction that up to 40 athletes would fail doping tests this Olympics was only an "off-the-cuff response" and an "arithmetic calculation" based on the figures from the 2004 Olympics.
Performance Enhancing Drugs and Steroids
The increased testing at the Olympics and stepped up pre-Games screening conducted at the national level have ensured cleaner competitions, he said.
"I can't comment exactly on what's going on at the Olympics until after," Howman said. "But, in general, I think we can say there has been a considerable enhancement in the fight due to WADA."
International Olympic Committee spokeswoman Emmanuelle Moro told ABCNews.com that 39 athletes who might have been caught doping in Beijing were caught prior to the Games because of improved pre-policing measures. In 2004, similar pre-Games testing prevented seven athletes from competing in Athens.
Still, anti-doping researchers remained unconvinced that Olympics testing efforts are keeping up with the cheats.
Tim Noakes, a professor of exercise and sports science at the University of Cape Town, South Africa, says that as long as undetectable drugs are available, the assumption is that they are being used.
"If there are fewer than expected positive doping tests, it really does not tell us that fewer athletes are doping," he wrote via e-mail. "It just says that fewer are using drugs that can be detected.
Cheating Olympic Athletes
"Observing the physiques of some successful athletes who have not tested positive suggests that they are using something that is not being detected."
Scientists are working around the clock at a drug-testing lab in Beijing to test for the methods and substances, such as stimulants, steroids, hormones and narcotics, banned by the World Anti-Doping Agency.
But, UCLA's Butch emphasized, athletes are increasingly seeking out short-acting drugs that clear the body very quickly. By monitoring the impact of those drugs on other molecules in the body, scientists have been able to catch cheaters.
Scientists determined last week, for example, that Spanish cyclist Maria Isabel Moreno had used the banned hormone erythropoietin. But because the drug exits the body rapidly it's often difficult for scientists to detect.
Other drugs that are eliminated quickly, Butch said, are composed of insulins and growth hormones. Gene doping is another method that might soon catch on.
Gene Doping Health Risks
Researchers say gene doping presents numerous health risks, such as leukemia and, even, death. But the anti-doping community believes athletes are eyeing it because of its ability to fly under the radar of doping tests.
In addition to the scientific hurdles associated with catching Olympic dopers, some experts say a monitoring structure that relies heavily on national anti-doping authorities also allows cheaters to evade detection.
"The Olympic testing process for performance enhancing drugs is a farce," Jamie Metzl, an executive vice president of the Asia Society, who has written extensively about international anti-doping efforts, told ABCNews.com in an e-mail. "[The process] cannot be successful because the tests are inadequate and often administered by national sports authorities with far stronger incentives to win than crack down on wrongdoers."