The World Anti-Doping Agency (WADA) has given clearance for anti-doping bodies to resume human growth hormone (hGH) testing after a more than year-long hiatus.
Routine testing was suspended in the wake of a judgement by the Court of Arbitration for Sport (CAS) in March 2013, in a case opposing the International Ski Federation (FIS) and Andrus Veerpalu, a retired Estonian cross-country skier.
The Court overturned a three-year ban for the skier on the grounds that, while the hGH test itself was reliable, it was not satisfied that the "decision limits" - the threshold beyond which a result constitutes an adverse analytical finding - were.
WADA has now published revised decision limits resulting from two new statistical analyses of a larger set of data.
The so-called hGH isoform test, first used at the Athens 2004 Olympics, has been designed to detect externally-administered growth hormone by measuring the ratio between two types of hGH isoforms; the administration of exogenous hGH gives rise to an elevated ratio.
The testing is done by using two distinct sets of reactive tubes coated with different combinations of antibodies; these are normally referred to as Kit 1 and Kit 2.
The revisions have marginally increased - from 1.81 to 1.84 - the male Kit 1 threshold; the Kit 2 decision limit has been increased more significantly, from 1.68 to 1.91.
Female decision limits have been set at 1.63 (Kit 1) and 1.59 (Kit 2) respectively.
With artificial hGH believed to be used by athletes on a wide scale to enhance performance, WADA encouraged samples to continue being collected even during the break in testing, for analysis once the revised guidelines were in place.
In its update, WADA says it has "taken the opportunity to remind anti-doping organisations (ADOs) that had previously stored blood serum samples for future hGH analysis that they should now proceed with retrospective analysis using the hGH isoform differential immunoassays test.
"In addition, ADOs that have conducted minimal blood testing have been asked to consider expanding their programmes to reflect the risk of hGH abuse by their athletes."
A new test to detect hGH abuse - known as the "biomarker test" - is understood to be under development.
This detects unnatural increases in two markers produced after the injection of hGH.
It is understood to be capable of detecting hGH up to two weeks after use, compared with more like 72 hours for the isoform test.
Contact the writer of this story at [email protected]
September 2012: Positive tests for HGH at London 2012 mark major breakthrough for dope busters
July 2012: New human growth hormone test added to doping police's armoury
September 2010: First athlete to test positive for HGH commits suicide