NOW that tickets for final sessions of the athletics competitions at Glasgow 2014 are all but sold out, speculation has arisen that the two biggest names in Commonwealth Games sport, Mo Farah and Usain Bolt, may be absent.

Asked about Glasgow next year, Farah said it would depend on how he recovered from the Virgin London Marathon. Since his debut in April's race has been a given since he signed a contract to run half of this year's event, that hardly constituted a revelation.

"It is not on my list," he said in a BBC interview to promote his autobiography. Mo is not daft. He knows the value of a good headline. And this was at least as attention-grabbing as one the previous week on a report in which the UK Athletics performance director, Neil Black, had said Farah wanted to double up at the Commonwealth Games and the European Championships.

The latter begin in Zurich on August 12, just 10 days after the final track event in Glasgow. Black said Farah was "open-minded and interested" in doing both championships, without specifying distances. It is hard to think Farah has misled his sport's leaders.

Marathons are a trip into the unknown: recovery can be problematic, so treat them with respect. Farah is doing precisely that, setting nothing in stone for next season, but he will not wish his ninth-place in the 5000 metres at the 2006 Games in Melbourne to be his Commonwealth career postscript.

I suggested some weeks ago that, subject to a sound marathon recovery, UK 1500m record-holder Farah might tackle the metric mile in Glasgow, and I still believe his participation there is likely.

Bolt, however, may not have matters wholly in his own hands. His career is without blemish, and his calm and measured control in the face of a relentless media doping inquisition is to his credit. Yet it is increasingly hard to justify his country's doping record.

Five elite Jamaican sprinters have tested positive for banned substances, including Asafa Powell (Bolt's predecessor as world 100m record-holder), Yohan Blake (100 and 200m runner-up to Bolt in London), 2012 women's 100m champion Shelley-Ann Fraser-Price, and former world 200m champion Veronica Campbell-Brown. Jamaica won eight of a possible 12 individual Olympic sprint medals, plus men's and women's 4 x 110m gold and silver in London, but no less than 18 of the Caribbean nation's sprinters have recently been implicated in adverse findings or have served suspensions.

That's a remarkable number for a nation of just 2.7 million. Russia has been pilloried for some 40 recently sanctioned athletes, but their population is more than 50 times that of Jamaica. The statistics have at last rung alarm bells with the World Anti-Doping Agency (WADA), and also taking into account lenient treatment of triple Olympic medallist Campbell-Brown, they are to conduct an investigation

A two-year ban was in order, yet she escaped with a warning from Jamaican authorities following a positive test for a diuretic notorious as a masking agent for steroids. The IAAF, the world athletics body, told The Herald they are reviewing the case. This could yet lead to suspension. But WADA's decision to conduct a "high priority extraordinary audit" of the Jamaican Anti-Doping Commission (JADCO) has more potentially serious repercussions. The former executive director of JADCO, Renee Anne Shirley, exposed a breakdown in their out-of-competition test programme. That's the one which really matters, as a drug-fuelled sprinter is unlikely to compete where testing is known to be done.

Shirley says only one out-of competition control was conducted by JADCO after February of the Olympic year. She was described by JADCO's chairman as "demented" and a "Judas". They claim she was fired because she had an agenda.

The IAAF told The Herald their programme is robust and thorough. It is, but it is not the IAAF whose competence is in question. They operate a registered testing pool of the international elite. It's drawn from the top 20 in each event.

Last year Jamaica had 19 athletes in that pool. They were tested 126 times (an average of 6.63 tests per athlete) making Jamaicans the most tested in the world. Nearest to Jamaica was the US (43 athletes tested 222 times, an average of 5.16 per athlete). Bolt was tested more than a dozen times.

When all tests under IAAF jurisdiction are combined, 37 Jamaican athletes were screened outwith competition. However Shirley's revelations expose a window of five months before London 2012 during which doping could have been done with near impunity. Disturbingly, Jamaica has refused to admit WADA inspectors until next year, during the run-in to the Glasgow Games. Jamaica should be suspended from competition until they comply. Already, weightlifting suspends whole nations from international competition for excessive breaches of doping rules. The IAAF may be forced to do likewise to maintain credibility.

So what if both Bolt and Farah should be absent from Hampden next year? I recall no uproar from Delhi when Bolt's absence from the 2010 Commonwealth Games became known. Or (other than in Scotland) when it emerged cyclist Sir Chris Hoy would not compete. Or the heptathlon champion Jessica Ennis, or 800m world record-holder David Rudisha.

Delhi delivered a memorable Commonwealth Games. Glasgow, I am certain, will do likewise. Winners' names will be recorded, and history will remember them. Not the identities of those who were absent. However, we are entitled to have confidence in the integrity of the system which screens athletes who compete in Glasgow.