Two different immunoassays produced highly discordant results when used to measure anti–Müllerian hormone in feline blood serum and urine

Anti-Müllerian hormone (AMH) is a useful biomarker for a variety of veterinary conditions relating to the gonads. For female mammals, these include spayed or intact status, ovarian remnant syndrome, granulosa cell tumor, and ovarian response to gonadotropin stimulation for assisted reproductive technologies. We compared 2 different AMH immunoassays that produced markedly discordant results, although the original aim of our research was to refine an earlier study that intended to determine whether AMH concentrations in feline blood serum and urine are correlated. The previous study reported measurable AMH concentrations in all 27 urine samples tested, which were not correlated with the corresponding serum concentrations. Our studies differ in that we used the AMH ELISA (assay A; AL-116, Ansh Labs) currently in use in our diagnostic laboratory, which differs from the immunoassay (assay B; E0078Ca, BT Lab) used in the original study. In contrast to assay B, assay A detected no AMH in urine collected from 19 cats immediately before ovariohysterectomy. We re-tested these same urine samples using assay B, and all had measurable AMH. However, a negative serum sample that is routinely run in assay A for quality control purposes also had measurable AMH in assay B. A second run of assay B found measurable AMH concentrations in 20 serum samples that had previously tested below the detection limit of assay A. Assay B also failed the parallelism validation test. Our results indicate that assay B is not valid for feline or canine AMH testing.