Inflammatory marker analysis of uterine cytobrush samples helps identify mares with endometritis

To evaluate inflammatory cytokine and chemokine concentrations in endometrial samples collected by cytobrush or swab as a potential screening diagnostic marker for equine endometritis.

88 mares had endometrial samples collected, which included cytobrush, swab, and/or biopsy. Clinical reproductive records, reproductive ultrasound examination, endometrial cytology and culture results, and biopsy grading score were recorded. Fluorescent bead-based multiplex assays for the inflammatory markers interferon-γ, interferon-α, IL-1β, IL-4, IL-10, IL-17A, soluble CD14, tumor necrosis factor (TNF)-α, C-C motif chemokine ligand (CCL)-2, CCL3, CCL5, and CCL11 were carried out from the endometrial cytobrush and swab samples in reproductively healthy mares and mares with endometritis in a prospective cross-sectional study.

The endometrial cytobrush technique yielded higher inflammatory marker concentrations for mares with endometritis than endometrial swabs. Tumor necrosis factor-α was increased in endometrial cytobrush samples from estrous mares that had endometrial neutrophils on cytology (n = 14; median, 4,185 pg/mL; IQR, 1,318.8 to 7,530 pg/mL) compared to samples from mares without neutrophils on cytology (n = 68; median, 1,653 pg/mL; IQR, 672 to 3,606.8 pg/mL; CI, 288 to 3,715) and in mares with endometritis (n = 14; median, 4,185 pg/mL; IQR, 1,318.8 to 7,530 pg/mL) compared to mares without endometritis (n = 57; median, 1,718 pg/mL; IQR, 651.5 to 3,968 pg/mL; CI, 580 to 4,383). Finally, mares with uterine TNF-α concentrations < 3,942 pg/mL in combination with CCL5 concentrations < 15,985 pg/mL had a 100% chance of identifying as a mare with a healthy endometrium.

Increased concentrations of TNF-α and CCL5 in endometrial cytobrush samples are identified in mares with inflammatory endometritis.

Inflammatory markers measured from endometrial cytobrush samples could be used to identify mares for endometritis that may have false negative results.