Doubts have been raised about the research paper that Chris Froome is using to defend his high reading for an asthma drug in the 2017 Vuelta a España.

Team Sky’s star tested over the allowed limit of asthma drug salbutamol after stage 18 on his way to winning the Vuelta overall in September. A judge should rule later this summer, possibly delivering Froome a ban and stripping his Vuelta a España title.

Froome and Team Sky have consistently denied any wrongdoing.

>>> Everything you need to know about Chris Froome’s salbutamol case

Froome, according to an article in May, is basing part of his defence on a published paper from the Centre for Human Drug Research in Leiden in the Netherlands. It recalibrated his reading from 2000 to 1429 nanograms per millilitre (ng/ml), much closer to the “actionable” threshold of 12.

It also said that WADA’s salbutamol test is unsafe given that levels in urine can vary wildly. As many as 15.4 per cent of the tests can could produce false positives and putting the presumption of guilt on the athlete is “completely unacceptable.”

The Daily Mail reported on Monday that the paper “is the subject of intense scrutiny” at the Union Cycliste Internationale (UCI) and that it simply could be a “delaying tactic” so that Froome can race for a fifth Tour de France in July. Also, the article pointed out that the Leiden research was carried out on dogs, not humans.

Another concern could be that one of the paper’s authors Adam Cohen is the editor at the British Journal of Clinical Pharmacology and could have had a say when deciding to publish the findings. The Daily Mail article also raised the point that author Jules Heuberger argued in 2017 that EPO does not affect an athlete’s performance.

The UCI’s anti-doping lawyers are combing though the pages, around 1500, of submitted documents by Froome and his legal team. The included Leiden paper does not seem to bother WADA when considering its salbutamol testing model.

“I read the article you refer to and no, no concern at all,” WADA’s science director, Dr Olivier Rabin said last month. “Nothing new as their model is based on three well-known studies. We believe the current threshold is solid considering the scientific literature published on salbutamol over the past 20 years.”

Rabin might have also looked at the impact score of the British Journal of Clinical Pharmacology. The article on Monday said that the ranking system for scientific publications lists it at 3.83. As an example, CA-A Cancer Journal For Clinicians has a 131.72 score.

Though some complain, Froome is free to race in the meantime due to the rules on specified or known substances that athletes take. Salbutamol is permitted, just that one cannot exceed a certain threshold.

Froome has already won the Giro d’Italia this season, and will be racing for a historic Giro/Tour double and fifth Tour title next month.

“It’s difficult for ordinary people to understand,” UCI boss David Lappartient said recently. “They say, ‘What are they doing at the UCI? They do not move ahead with the case. Yes but this case is much more complex than others. And perhaps he has more means to demonstrate this complexity precisely, where others might have given up for not being able to carry out more cumbersome procedures.”

Froome explained after his Giro win: “Once the time is right, we will share the information with everyone, and I am sure they will see it from our point of view.”