The use of a dipstick assay for Early Pregnancy Factor (EPF) to detect pregnancy in dairy cattle

Over a two month period, a test for an Early Pregnancy Factor (EPF) was used on milk and peripheral blood samples taken from 159 cows at day 7 after breeding and in 154 of those cows at day 17. In maternal peripheral serum samples 154 (97%) were positive at day 7 and 146 (95%) at day 17. In milk samples 38 (24%) were positive at day 7 and 33 (22%) at day 17. These results were compared to transrectal ultrasound pregnancy detection at day 28-35 post-breeding. The sensitivity on serum samples at day 7 was 97% and the specificity 3%. At day 17 the sensitivity was 96% and the specificity 6%. The sensitivity for milk samples was 14% on day 7 with a specificity of 69%, whilst the sensitivity was 24% and the specificity 81% at day 17. A Kappa statistic was calculated and presented with a 95% confidence interval (95% CI) to compare the results of the ECF tests and the detection of pregnancy by ultrasound scan. Values below 0.4 were considered to indicate poor agreement. Between ECF test and ultrasound scan results, between 0.4 - 0.6 fair, between 0.6 - 0.8 good and over 0.8 very good agreement (Thrusfield, 1995). In relation to pregnancy detection by ultrasound, Kappa values did not exceed 0.05 for milk and, or, serum on day 7 and, or, day 17, individually or in combination. It was concluded that this was not a reliable test for pregnancy at day 7 or at day 17.