PARIS — The head of cycling's world governing body opposes retesting further samples to check for the blood-boosting drug found among four Tour de France riders.

The Chatenay-Malabry laboratory outside Paris rechecked samples from this year's Tour after a new test became available to detect CERA, an advanced version of EPO. Bernhard Kohl, Stefan Schumacher, Riccardo Ricco and Leonardo Piepoli all tested positive.

The French anti-doping agency is now willing to retest samples from the 2007 Tour and this year's Giro d'Italia and Spanish Vuelta.

But International Cycling Union president Pat McQuaid is against the idea.

"From the UCI's point of view, we prefer to look forward rather than look backward," McQuaid said in an interview with The Associated Press on Monday. "To randomly say 'OK, let's take all the samples from 2007 from the Tour de France and put them all through testing processes' ... it's futile, it's expensive and it's not going to serve the purpose in the anti-doping fight of today."

The UCI carried out all the testing at the 2007 Tour, but a rift with Tour organizer ASO meant the French anti-doping agency took sole charge of testing at this year's Tour — with a marked increase in blood testing.

McQuaid thinks retesting samples from other races, including the Giro and the Vuelta, would lead to chaos.

"If we're going to start rejigging the podium of every major international race over the past two or three years, by finding new tests for new products, and going back to the organizer and saying 'you've got to rejig your podium' .. it makes a complete mockery of sport," he said. "You need very good information in order to do that in the first place."

McQuaid, speaking before a ceremony in Paris to honor 2008 Pro Tour winner Alejandro Valverde, questioned whether it would even be possible to retest old samples.

"I couldn't give you an answer as to where the 2007 samples are, nor whether they are adequate for the testing," McQuaid said. "The Giro is already over four or five months (ago). I don't know whether the samples are still (valid), whether they've degraded to an extent ...

"It's very difficult to detect CERA in urine samples. I don't know about the blood samples, what the situation is there. As I say, I prefer that we move forward, rather than move backward."

The International Olympic Committee said earlier this month that it will retest samples from the Beijing Games for CERA.

Pierre Bordry, head of the French anti-doping agency AFLD, said he passed all the information regarding how to do CERA tests to the UCI at the end of August so that the world body could use the testing method at the Vuelta.

"The testing program was available," Bordry said, adding that he was unsure whether it was implemented at the Vuelta, which ended Sept. 21.

"That wouldn't be a decision of the UCI to do that. It's outside of our scope," McQuaid said.