Comparative evaluation of two commercial pregnancy-associated glycoproteins tests for early detection of pregnancy in dairy cattle

The aim of this study was to determine and compare the diagnostic accuracy of two pregnancy-associated glycoproteins tests (IDEXX on-farm pregnancy test [OFPT] and IDEXX rapid visual pregnancy test [RVPT]) for early pregnancy diagnosis in dairy cattle. Blood samples were collected from Holstein cows (n = 317) by coccygeal venipuncture 28-31 days after artificial insemination (AI). The OFPT and RVPT were performed on the farm within 2 h after blood collection using whole blood or blood serum. Transrectal ultrasonography (USG) was performed for pregnancy diagnosis on day 32 post-AI as a gold standard. One-hundred fourteen cows were diagnosed as pregnant and 203 were determined to be nonpregnant. Furthermore, embryonic mortality was detected in four of the nonpregnant animals, based on fragmented/dispersed embryonic membranes and the absence of heartbeat. Sixteen and 14 false positive results (13 jointly for both tests) were obtained for the RVPT and OFPT, respectively. Three false negative results were obtained for the RVPT. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy for the OFPT were 100%, 93.1%, 89.1%, 100% and 95.6%, and for RVPT were 97.4%, 92.1%, 87.4%, 98.4% and 94.0%, respectively. The ability of both tests to distinguish between pregnant and open cows was very good (AUC of both tests above 0.9). The OFPT and RVPT almost perfectly agreed with each other. According to McNemar's analysis, false positive results have been caused difference between the two pregnancy tests and USG. In conclusion, both the RVPT and OFPT proved to be reliable and practical methods for pregnancy diagnosis 28-31 days after AI in dairy cows. However, the results of both pregnancy tests were affected by the occurrence of embryonic mortality around the time of their employment.