The Accuracy and Reproducibility of the Endometrial Receptivity Array Is Superior to Histology as a Diagnostic Method for Endometrial Receptivity

In the same set of endometrial biopsies, the accuracy of the endometrial receptivity array diagnostic tool was superior to dating by endometrial histology, and was reproducible in the same patients 29–40 months later.


Patricia Díaz-Gimeno, Ph.D., Maria Ruiz-Alonso, Ph.D., David Blesa, Ph.D., Nuria Bosch, M.D., José A. Martínez-Conejero, Ph.D., Pilar Alamá, M.D., Nicolás Garrido, Ph.D., Antonio Pellicer, M.D., Carlos Simón, M.D.

Volume 99, Issue 2, Pages 508-517, February 2013



To compare the accuracy and reproducibility of the endometrial receptivity array (ERA) versus standard histological methods.


A comparative prospective study (May 2008-May 2012).


University-affiliated infertility clinic.


Eighty-six healthy oocyte donors, regularly cycling, aged 20-34 years with a BMI of 19-25 kg/m2.


Endometrial biopsies were collected throughout the menstrual cycle. For the accuracy study, seventy-nine 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 histological and ERA dating. For the reproducibility study, seven women undergo ERA test and it was repeated in the same patients on the same day of their cycle 29 to 40 months later.

Main outcomes measured:

Concordance of histological and ERA dating related to LH as a reference, and inter-observer variability between pathologists were statistically analysed by the quadratic weighted Kappa index. ERA reproducibility was tested and its gene expression visualized by PCA analysis.


For each pathologist, concordance against LH peak yielded values of 0.618 (0.446-0.791) and 0.685 (0.545-0.824) respectively. Inter-observer 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.


The ERA is more accurate than histological dating and is a completely reproducible method for the diagnosis of endometrial dating and the receptivity status.

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