Endometritis in the mare: A diagnostic study comparing cultures from swab and biopsy

The objective of this study was to compare results from endometrial culture swabs with results from culturing of endometrial biopsies. The culture results were related to cytological findings (polymorphonuclear; PMN-cells) and histological observations (PMN-cells). Biopsy and swab samples were smeared on the surface of a blood agar petri dish, and examined for growth of bacteria. Cytology samples were obtained from endometrial biopsies, stained and examined under microscopy for the presence of PMN-cells. Endometrial biopsies were examined for the presence of PMN-infiltration of the endometrial luminal epithelium and the stratum compactum. Using the presence of PMNs in a tissue specimen as the “best standard” for diagnosing endometritis, the sensitivity of bacterial growth from an endometrial biopsy was 0.82. The sensitivity for cytology was 0.77, and the sensitivity of bacterial growth from an endometrial surface swab was 0.34. The specificity for biopsy cultures, swab cultures, and cytology to diagnose endometritis were 0.92, 1.0, and 1.0 respectively. The positive predictive value for biopsy cultures, swab cultures, and cytology were 0.97, 1.0, and 1.0 respectively. The negative predictive value for biopsy cultures, swab cultures, and cytology were 0.67, 0.44, and 0.62 respectively. In conclusion, bacteriological culture and cytology from an endometrial biopsy provide the practitioner with the most accurate results regarding both sensitivity and positive predictive value.