World Athletics president Sebastian Coe said gene testing for women athletes had been a "largely successful operation" at the world championships in Tokyo, vowing that the process was here to stay.
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Track and field's governing body carried out testing for the SRY gene, which is part of the Y chromosome and causes male characteristics to develop.
Athletes who test negative for the Y chromosome are eligible to compete in the women's category in world ranking competitions.
If the test is positive, athletes can only compete in the women's category in non-world ranking competitions or in a category other than that.
"The SRY test was absolutely the right thing to do if you are committed to promotion and preservation (of) and protecting the female category," Coe told a press conference on the final day of action in Tokyo.
"There should be no ambiguity about that in any organisation in sport in the world, then you do everything you possibly can that gives practical application to that and not just warm words.
"That test was an absolutely essential element in the principle and the philosophy that we hold here at World Athletics."
Athletics has long wrestled with eligibility criteria for women's events, amid questions over biological advantages for transgender athletes and those with differences of sex development (DSD).
Transgender women who have gone through male puberty are banned by World Athletics from women's events. The federation requires women DSD athletes, whose bodies produce high testosterone levels, to take medication to lower them in order to be eligible.
100% TESTED
World Athletics has said its gene test – carried out using a cheek swab or blood test – is "extremely accurate," which means false positives or false negatives are "extremely unlikely".
"Let me be clear, the gene test is here to stay," said Coe.
"It's a one-off test. So an athlete takes that test, they never need to take that test again. Throughout the course of their career, we'll have a new cohort of athletes every year that will need to be tested.
"It was largely a successful operation. We set out to test everybody by the time we got into these championships... we got 100 per cent of them tested."
Coe said he appreciated questions about security of data.
"We were testing simply for the presence or otherwise of the Y chromosome," said the two-time Olympic 1 500m gold medallist for Britain.
"It wasn't about genetic testing. Broader than that, it wasn't about DNA.
"When the data, the test is validated, the data is destroyed."
Coe added that support for the tests had been overwhelmingly positive, notably from women athletes.
"Actually we had very few athletes that had any doubts about the importance of doing that," he said.
"Overwhelmingly, women athletes supported it, and I'm really grateful that so many member federations were able to help expedite the tests, our area associations as well, and sport came together on that."
ONE MORE WORLD RECORD FROM DUPLANTIS AND THERE'S NO CHRISTMAS PARTY, JOKES COE
World Athletics president Sebastian Coe joked Sunday that one more record from Armand 'Mondo' Duplantis would see track and field's governing body lose its Christmas party.
Duplantis set a new world record of 6.30 metres as he sensationally defended his world pole vault title in Tokyo on Monday, bagging $70 000 for the win and a further $100 000 for the new best mark.
The Swede had already wrapped up the competition with a winning vault of 6.15m before raising the bar another 15cm.
Duplantis went clear on his third attempt in what was his 14th world record in a discipline in which he is totally dominant. It was his fourth world record in 2025 alone.
Summing up what he dubbed "nine days of just outstanding athletics" and a "championships of the ages", Coe said: "My memory is not just the Mondo world record.
"I have actually told him that one more world record, World Athletics loses its Christmas party, two more world records we lose the summer party!
"There are 105 people hoping that we don't have too many more world records at this juncture."
Coe then added: "But of course, the ultimate we hope he can deliver as he always does."
The stand-out from that evening, the two-time Olympic 1 500m gold medallist insisted, was "the 57 000 people who remained in the stadium with only a field event" running at the time.
"Not one of them left at the end of that track session, I wanted to stay on.
"And then we also did find ourselves politely suggesting that some of them might want to leave half an hour after the world record and sort of go home.
"That's a high-class problem to have, believe me."
SURVIVORS' CLUB
Coe was also an interested spectator on Saturday for the men's 800m, sat alongside Kenya's current world record holder David Rudisha.
Rudisha set the mark of 1min 40.91sec when winning gold in the two-lap race at the 2012 London Olympics.
But this season, for the first time in a decade, a raft of athletes led by newly-crowned world champion Emmanuel Wanyonyi are threatening Rudisha's iconic mark.
Coe, himself a two-time Olympic silver medallist over the two-lap race and whose best of 1:41.73 still puts him joint eighth on the all-time list, said he and Rudisha were members of the "survivors' club".
"It was actually quite amusing because I sat watching it with David Rudisha," said Coe.
"We both hugged each other at the end of it, saying we're survivors. His world record survived, my British record survived," with Briton Max Burgin finishing sixth in 1:42.29.
Coe added: "We weren't sure actually at the start of it about both, although I was pretty sure I thought my British record was probably within striking distance. I didn't think David would end up at the end of the evening empty handed.
"We were the survivors' club last night. But no, it was a great race. And again, you couldn't write the script right until the last moment.
"They committed. They went through in 49 and bits. We both looked at each other, it was world record pace.
"But then, absolutely at the same moment, absolutely unscripted, we both went 'No'. That was at about 550m.
"We started to thinking well, our records are intact. Now we can really watch the race.
"It was a good evening all around and a proper 800m."