VANCOUVER, British Columbia — As the Vancouver Olympics draw to a close, one of the most striking statistics after two weeks of competition is zero.

That's how many athletes have been disqualified for positive drug tests, testament perhaps to the deterrent effect of the most stringent anti-doping program in Winter Games history.

Out of nearly 2,000 planned tests, the only doping violation so far has been minor — a female Russian hockey player was reprimanded after testing positive for a light stimulant contained in a decongestant before the games.

"There is nothing sensational to report," said Arne Ljungqvist, head of the International Olympic Committee's medical commission. "We are finding not very much indeed. It seems promising."

A few hundred more tests will be conducted over the final weekend of the games, with those results known early next week.

Could these games really be drug-free? Don't bet on it.

"I'm a realist. I'm not naive," IOC president Jacques Rogge said. "The final judgment will come in 2018."

The IOC stores doping samples for eight years so they can be tested retroactively for drugs that were undetectable at the time of the games. If future testing shows an athlete cheated, the IOC can impose sanctions and strip any medals.

That was the case last year, when the IOC retested samples from the 2008 Beijing Olympics and nabbed five athletes for using CERA, a new blood-boosting substance. Bahrain's Rashid Ramzi was stripped of his gold in the 1,500 meters.

"Clearly there has been a deterrent effect here for taking the drugs that are on the banned list," Rogge said. "I'm happy that athletes were wise not to use those 'classic' substances. But it does not mean we will not need to retest at a later stage."

Rogge said the current testing program still can't catch athletes conducting their own blood transfusions or detect designer performance-enhancers that aren't yet known to anti-doping scientists.

"Retesting will help us in that," he said. "But all our experts say they do not expect there are many drugs being used today that we do not know about."

As of Thursday, the IOC had conducted 1,821 tests — 1,426 urine, 395 blood — since the athletes' villages opened Feb. 4. Athletes were subject to out-of-competition tests at any time and any place. In addition, all medalists were tested after each event, along with two others at random.

Ljungqvist said Thursday the Vancouver doping lab would take an extra look at some blood samples. He said there was "a low-grade suspicion at a very low rate" that some samples could indicate new versions of EPO, a hormone that increases oxygen-producing red blood cells in the system.

"There is not a particular suspicion directed towards a particular athlete," Ljungqvist said. "But we, just to make sure, wish to follow up some blood data. And that means that we are looking at perhaps cases that are maybe using late generations of EPO."

Not everyone thinks the absence of positive tests is a sign the Olympics are getting cleaner.

Dr. Charles Yesalis, a professor emeritus at Penn State University and one of the foremost experts on steroids, is among the skeptics.

"It means zero to me. I interpret it the same way I interpreted the 1980 Olympics in Moscow, when they said they had no positives," Yesalis said in a telephone interview. "I'm sorry, it's laughable."

He said there was no reason to believe the doping problem was any better than it was 10 or 15 years ago.

"In this day and age, anybody who believes that elite sport is clean, God bless you, but I've been doing this for over 30 years, and my prognostication has been a bit better than the optimists," Yesalis said.

In the 11 previous Winter Olympics since drug-testing began, there were only 13 positive cases, seven of them at the 2002 Salt Lake City Games.

There was only one positive at the 2006 Turin Games. Russian biathlete Olga Pyleva was stripped of a silver medal after testing positive for a banned stimulant. She returned to the Olympics in Vancouver under the name of Olga Medvedtseva and won gold in the women's relay.

During the Turin Games, Italian police raided the lodgings of the Austrian cross-country and biathlon teams, seizing blood doping equipment. No Austrians tested positive in Turin, but a year later the IOC banned five of them for life for involvement in the scandal.

Ljungqvist attributes the absence of positive cases in Vancouver to increased pre-games testing by international sports federations and national anti-doping bodies.

"They are identifying drug takers at an earlier stage," he said. "The cheats are out before they arrive."

World Anti-Doping Agency president John Fahey said earlier that more than 30 athletes had been prevented from coming to Vancouver after being caught for doping violations in recent months.

In addition to standard Olympic drug tests, the international ski and biathlon federations have conducted their own pre-race screenings to check for irregular blood levels. The tests are designed as a health measure, but can indicate signs of doping.

Three competitors — Nordic combined athlete Niyaz Nabeev of Russia and cross-country skiers Kaspar Kokk of Estonia and Benjamin Koons of New Zealand — were suspended from competition for five days because of high hemoglobin levels but were reinstated after passing new tests.

Russian athletes in particular have been under scrutiny in Vancouver after more than half a dozen biathletes and cross-country skiers were suspended in the past year for using EPO.

Rogge said he spoke to Russian President Dmitry Medvedev and urged him to crack down on the doping problem.

In a related development, Russia's Kontinental Hockey League signed an agreement with WADA in Vancouver on Thursday pledging to implement tough anti-doping programs and comply with the agency's global anti-doping code.

"This sets an example for other major professional leagues that have not yet implemented code-compliant anti-doping programs," Fahey said.

The biggest doping news during the Olympics came from not Vancouver but Britain, where a rugby player — Terry Newton — became the first athlete suspended for using human growth hormone.

Ljungqvist said HGH is more likely to be used out of competition than during an Olympics, but he hopes a more advanced test will be in place for the 2012 London Games.

No matter how many drug cheats are caught or how few positive cases are recorded, the IOC is not about to declare victory.

"I do not speak in terms of winning a war," Ljungqvist said.