The IAAF has refuted fresh doping allegations after it was claimed athletics' world governing body turned a blind eye to suspicious blood tests involving 150 athletes, including a leading Briton.
German TV broadcaster ARD reported that a long-time member of the IAAF's medical commission, whose identity has not been revealed, had a list of dozens of questionable blood values which were not followed up.
The alleged cases involved blood samples taken between 2006 and 2008 and were "highly suspicious" according to the unnamed medical commission member, but there was no follow-up involving target testing of the athletes involved by the IAAF's doping department.
But the chairman of the IAAF medical and anti-doping commission Dr Juan Manuel Alonso said on Twitter that "blood samples taken before 2009 were thoroughly examined".
The IAAF stressed in an official statement that a member of that commission would not know whether follow-up tests had been conducted or not and said it was not possible to conclude whether an athlete had doped "on the basis of one single blood value".
It is claimed by ARD that many of the samples in question came from Russian athletes, but that three British athletes were also involved along with others from Kenya, Germany, Spain and Morocco.
ARD has also alleged there is systematic doping in Russian athletics and implicated the IAAF in covering up the problem.
The British trio are included on a list of names which appears to have come from the IAAF and is headed "Suspicious".
In responding to the allegations, the IAAF also pointed out it only launched the athlete biological passport in 2009, meaning before that date there was no "harmonised regulatory framework allowing the use of reliable and comparable values".
It said blood data collected before 2009 was used for target purposes to "trigger" follow-up urine tests for EPO detection and abnormal results were followed up "whenever possible logistically".
Alonso added on his personal Twitter account that "some athletes were caught" in this way.
The IAAF also said it had used blood values prior to 2009 as "secondary evidence" to support an increased sanction for an athlete who doped, but said they did not have "the same level of reliability and strength as the post-2009 values which were collected under strict and stringent conditions".
It also said it used the pre-2009 blood data to conduct a prevalence study which was published in 2011 and allowed the IAAF to identify the countries where there was a high risk of doping.
