The Anti-Mullerian hormone (AMH) or egg timer test is used to measure ovarian reserves and has been popular in Australia for more than a decade with women seeking it out to assess their fertility.

The medical director of fertility group Genea, Mark Bowman, said health experts had always warned women that while the AMH test can give an indication of ovarian reserves, it was not a fail safe test of potential fertility.

“While the number of eggs a woman has left is important to her ability to conceive, equally so is the quality of her eggs,” Associate Professor Bowman said.

Since 2011, the standard test for AMH has been the Beckman Coulter Generation (Gen) II assay, but in July 2013 the testing protocol was revised after a spate of false low readings.

“We, along with other fertility clinics, realised that some of the low readings that were coming back were significantly out of step with our expectations so the testing protocol was assessed and revised in July 2013.”

A study conducted from 2012 to 2015 by scientists and doctors from Genea and published in the latest edition of the Journal of Assisted Reproduction and Geneticscompared the original testing protocol with the revised protocol and found that the original protocol significantly underestimated results, by an average of 68 per cent.

In the study, AMH levels were measured for 492 natural conception women aged between 20 and 44 years using the original and revised Gen II test. The comparison found the original protocol significantly underestimated AMH levels.

In all samples with detectable AMH levels, the revised protocol yielded a higher concentration compared with the original protocol, the magnitude shift ranging from 3.4 to 283.3 per cent (median 68.0 per cent). This study is also the first to publish a reference range for AMH based on natural conception levels.

“While the faulty protocol has been replaced and Genea is using the new and fully automated protocol, this is the first study which assesses the impact on the Australian population. It shows that many of those thousands of Australian women who undertook an AMH test between 2011 and mid-2013 were potentially given falsely low results,” Assoc Prof Bowman said.