Reliability of AMH in Serum after Long-term Storage at -80°C and an Extended Thawing

Background: Measurement of anti-Müllerian hormone (AMH) is a valuable clinical tool for evaluating ovarian function. The present study aims to evaluate the reliability of AMH measurements obtained from samples kept for long-term storage with or without intermittent thawing. Methods and findings: Serum samples from 35 young female cancer patients were prospectively collected and stored at -80°C from 2007 until 2010. In 2011, AMH was analyzed with the DSL assay. During storage, the samples were exposed to a freezer error in 2013 that resulted in their being thawed up to 11°C for a maximum of 21 days and then refrozen. In 2014, the same samples (new aliquots) were analyzed with the Ansh-AMH assay. To test the reliability of the results from 2014, we conducted a thawing experiment on serum samples from 10 randomly selected females and compared the Ansh-AMH results for samples stored in a freezer with aliquots from the same samples that were stored at 11°C for 1, 3, 7, 14, and 21 days, respectively. Average AMH levels were 1.6 times higher when assayed with the Ansh-AMH compared with the DSL-AMH, which is in line with reported agreement between these types of assays. The same difference between the assays was found in samples that differed two years in storage time. The Ansh-AMH levels from ten serum samples without long-term storage were not influenced by exposure to 11°C for up to 21 days. Conclusions: The results indicate that long-term storage at -80°C and episodes of thawing have little impact on AMH levels analyzed with current methods. These data are reassuring and enable longitudinal studies to be planned that will analyze all collected serum samples simultaneously.