The accuracy and reproducibility of the endometrial receptivity array is superior to histology as a diagnostic method for endometrial receptivity

ObjectiveTo compare the accuracy and reproducibility of the endometrial receptivity array (ERA) versus standard histologic methods.DesignA comparative prospective study (May 2008–May 2012).SettingUniversity-affiliated infertility clinic.Patient(s)Eighty-six healthy oocyte donors, regularly cycling, aged 20–34 years with a body mass index (BMI) of 19–25 kg/m2.Intervention(s)Endometrial biopsies were collected throughout the menstrual cycle. For the accuracy study, 79 samples were grouped into two cohorts: the training set (n = 79) for ERA machine-learning training and dating, and a dating subset (n = 49) for comparison between histologic and ERA dating. For the reproducibility study, seven women underwent ERA testing and it was repeated in the same patients on the same day of their cycle 29–40 months later.Main Outcome Measure(s)Concordance of histologic and ERA dating related to LH as a reference, and interobserver variability between pathologists were statistically analyzed by the quadratic weighted Kappa index. The ERA reproducibility was tested and its gene expression visualized by principal component analysis.Result(s)For each pathologist, concordance against LH peak yielded values of 0.618 (0.446–0.791) and 0.685 (0.545–0.824). Interobserver variability between pathologists yielded a Kappa index of 0.622 (0.435–0.839). Concordance for ERA dating against LH peak showed a value of 0.922 (0.815–1.000). Reproducibility of the ERA test was 100% consistent.Conclusion(s)The ERA is more accurate than histologic dating and is a completely reproducible method for the diagnosis of endometrial dating and receptivity status.