The reliability of the histological diagnosis of endometritis in asymptomatic IVF cases: a multicenter observer study

Chronic endometritis is associated with abnormal uterine bleeding, recurrent abortion and infertility. It is a subtle condition, and therefore is difficult to diagnose. The diagnosis is ultimately based on the presence of plasma cells in the endometrial stroma on histopathological examination. Literature on the reproducibility of the diagnosis of chronic endometritis is lacking. Therefore, the aim of the current study was to assess the interobserver agreement of two pathologists in diagnosing chronic endometritis in asymptomatic, infertile patients.

In the context of a randomized controlled trial, an endometrial biopsy was taken during a screening hysteroscopy prior to IVF. All endometrial samples were independently examined by two pathologist. The slides diagnosed with chronic endometritis were replenished with a random sample of the remaining slides up to a total of 100, then exchanged between the two pathologists and reassessed.

Of the 678 patients who underwent hysteroscopy, 19 patients were diagnosed with at least possible chronic endometritis (2.8%). Perfect agreement between the pathologists, before and after inclusion of 13 slides with additional immunohistochemistry staining, was found in 88 and 86% of reviews, respectively. The interobserver agreement was substantial, with kappa-values of 0.55 and 0.66, respectively.

The interobserver agreement in diagnosing chronic endometritis in asymptomatic infertile patients was found to be substantial. Although the diagnostic reliability is sufficient with the methods in the present study, the low prevalence and unknown clinical significance of endometritis warrants further study.