[Diagnostic value of minimal endometrial sampling combined with CD138+MUM-1 dual immunostaining for chronic endometritis in FET cycles: a propensity score matching retrospective cohort study].

Objective

To evaluate the prevalence of endometrial stromal plasma cell infiltration in infertile women undergoing frozen-thawed embryo transfer (FET), assess the ability of routine non-invasive clinical indicators to identify plasma cell infiltration, explore plasma cell thresholds using minimal endometrial sampling combined with cluster of differentiation 138 (CD138)+multiple myeloma antigen 1 (MUM-1) double immunohistochemical staining for chronic endometritis (CE), and analyze pregnancy outcomes after standardized treatment.

Methods

Infertile women scheduled for FET between March 2023 and March 2025 at Guangdong Provincial Hospital of Chinese Medicine were enrolled. Patients were divided into biopsy (n=117) and non-biopsy groups (n=919). Endometrial samples in the biopsy group were examined using CD138+MUM-1 double immunohistochemical staining, and patients with at least one dual-positive plasma cell received standardized antimicrobial treatment. Logistic regression was used to analyze factors associated with plasma cell infiltration. Propensity score matching (PSM) was applied to balance baseline characteristics between the two groups, and pregnancy outcomes were compared.

Results

A total of 1 096 patients with 1 483 embryo transfer cycles were included, including 177 patients in the biopsy group, 113 cases were dual-positive plasma cell, the plasma cell infiltration positivity rate was 63.8% (113/177); and the post-treatment conversion-to-negative rate was 86.2% (81/94). No significant associations were found between plasma cell infiltration and age, body mass index, anti-Müllerian hormone level, duration of infertility, or reproductive history (all P>0.05). After PSM, the pregnancy rate was significantly higher in the biopsy group (180 cycles) than that in the non-biopsy group (463 cycles), the pregnancy rates were 56.7% (102/180) vs 45.1% (209/463; P=0.009); subgroup analyses showed significantly improved pregnancy rates in patients with 1-4 or 5-10 plasma cells (all P<0.05). Miscarriage rates did not differ significantly between the two groups (P>0.05).

Conclusions

Routine non-invasive clinical indicators are insufficient for identifying CE. Minimal endometrial sampling combined with CD138+MUM-1 double immunohistochemical staining has substantial diagnostic value, and even low-level plasma cell infiltration (1-4 cells) may be clinically meaningful. Targeted endometrial histological assessment and standardized treatment in patients likely to benefit may improve pregnancy outcomes.