Consistency of endometrial receptivity array and histologic dating of spatially distinct endometrial samplings: a prospective, blinded study

Objective: To compare the consistency of endometrial receptivity array (ERA) and histologic dating among 3 spatially distinct endometrial samples obtained during a cycle of exogenous estrogen and progesterone. Design: Prospective blinded study. Setting: University practice. Patients: Twelve patients undergoing a mock frozen embryo transfer cycle. Intervention: Endometrial biopsy was performed in a manner that provided a spatially organized endometrial specimen, corresponding to the fundus, middle, and lower segment. Each of these 3 sections was further divided into immediately adjacent specimens for ERA and histology. Main Outcome Measure: Consistency of the ERA and histology results among fundal, mid, and lower endometrial biopsy specimens. Results: The ERA showed variability in outcome among different patients but dated all specimens originating from the same patient identically. Histologic dating showed variability between patients as well as between different locations within the uterus. When comparing average dating results for each patient, we saw a positive correlation between histologic and ERA dating (Spearman Rho = 0.45); however, this did not reach statistical significance. The ERA results from upper, mid, and lower uterine biopsy specimens were identical for each autologous biopsy, whereas histologic dating showed variability with an average standard deviation of 0.71 days. Conclusions: The increased heterogeneity of histologic dating is likely to be attributed to the subjectivity of the test. Furthermore, we did not observe a consistent lag or advancement in histologic or ERA dating between the fundal or lower uterine biopsies. Overall, clinicians should be reassured that endometrial tissue will return consistent ERA results independent of the location within the uterus in which it was obtained.