Comparison of a commercial bovine pregnancy-associated glycoprotein ELISA test and a pregnancy-associated glycoprotein radiomimmunoassay test for early pregnancy diagnosis in dairy cattle

The present study aimed to compare the accuracy of a commercial PAG-ELISA test (Bovine Preg Test 29) and bovine pregnancy-associated glycoprotein radioimmunoassay (PAG-RIA) for diagnosing pregnancy at Day 28 after insemination in dairy cows. Transrectal ultrasonography (TRUS) was performed in 100 Holstein-Friesian cows at Day 28 after artificial insemination (AI; Day 0) to diagnose pregnancy. After TRUS examination, blood sample was collected from the coccygeal vessels of each cow to measure the concentrations of bPAGs by PAG-RIA test and Bovine Preg Test 29. Milk samples were collected at Days 0, 21 and 28 for measurement of progesterone (P4) by ELISA test. The cows were re-examined by TRUS at Day 42 to confirm the pregnancy diagnoses. The actual gold standard was based on TRUS outcomes at Day 28 that agreed with the outcomes of PAG-RIA test or PAG-ELISA test. If the outcomes of TRUS at Day 28 and PAG-RIA test and PAG-ELISA test did not agree, the gold standard was based on the outcome of TRUS at Day 42. Out of 100 inseminated cows, 41 were confirmed pregnant at Day 28 after AI. Based on the actual gold standard, the sensitivity of TRUS, PAG-ELISA and PAG-RIA tests for diagnosing pregnant cows at Day 28 were 92.7%, 90.2% and 100%, while the specificity of the three tests for diagnosing non-pregnant cows were 91.5%, 98.3% and 94.4%, respectively. The overall accuracy of the three tests were 92%, 95% and 97%, respectively. The degree of agreement (Kappa±S.E.) between PAG-RIA and PAG-ELISA test was 0.90 ±0.04. The degrees of agreement between PAG-RIA and PAG-ELISA and TRUS at Day 28 were 0.80±0.05 and 0.76±0.06, respectively. In conclusion, the commercial PAG-ELISA test is a highly accurate method for diagnosing early pregnancy in dairy cows on Day 28 after AI and may be used as an alternative method to the TRUS and the PAG-RIA test.