161 COMPARISON OF DIFFERENT DIAGNOSTIC METHODS IN EQUINE ENDOMETRITIS

Abstract

Prolonged endometritis is the most common cause of infertility in mares causing great economic impact. Many mares fail to be diagnosed with endometritis despite the availability of different diagnostic tests. Therefore, the purpose of this study was to compare endometrial swab, low-volume lavage (LVL) and endometrial biopsy as diagnostic methods for endometritis and to report the prevalence of this disease in a referral practice population. Fifty-one mares presenting for routine breeding or infertility work-up were examined by transrectal ultrasonography, before collecting samples for endometrial culture and cytology. Seven of the 51 mares had all the tests except endometrial biopsy. A mare was classified positive for endometritis if she demonstrated two or more of the following 5 criteria on a checklist (new gold standard; NGS): (1) abnormal clinical findings (any of uterine fluid on ultrasound, or excessive oedema for follicular size, or history of subfertility); (2) abnormal gross character of the LVL fluid: (cloudy, discolored, debris) before centrifugation; (3) positive endometrial cytology (≥1 neutrophil per high power field, or ≥1% (1 : 100) neutrophil to epithelial cell ratio on cytology); (4) bacterial growth on culture of the LVL pellet; and (5) histological evidence of inflammation (acute, chronic, and mixed) detected on endometrial biopsy. Data were analysed via kappa coefficient (k) and frequencies were calculated for sensitivity and positive predictive value (PPV) with biopsy being the gold standard and compared to the NGS. Endometritis was diagnosed in 35/44 (79.5%) mares by biopsy (5/35 had acute endometritis, 12/35 had chronic; 18/35 had a combination of acute and chronic endometritis). Based on the endometritis criteria (2/5 items on the checklist), 33/51 (64.7%) mares were diagnosed to have endometritis. All 11 of the barren mares were diagnosed by the checklist, while two of these 11 mares had no evidence of endometritis by biopsy, but had clinical signs or cloudy efflux. The character of the endometrial flush was 45% sensitive (k = 0.046), while culture was 22% sensitive, when compared to endometrial biopsy. When each criterion for endometritis was compared against the NGS, endometrial biopsy was the most sensitive diagnostic method (sensitivity = 86%). Abnormal clinical findings showed moderate agreement with the NGS (k = 0.4138), with a sensitivity of 62% and P = 0.0019. Positive endometrial cytology showed similar agreement (k = 0.3761), and sensitivity (sensitivity = 64%, and P = 0.0069). These studies have also shown the importance of using laboratory data in light of clinical findings, since they have shown that no test by itself is sensitive enough to diagnose a mare with subclinical endometritis, and that this disease might be under diagnosed. Since this study was performed in a referral hospital, there may have been a higher prevalence of endometritis than found in general clinical practice. An endometritis checklist could be used in cases where endometrial biopsies are not readily available.