Montgomery M E, Leslie K E, Martin S W
Can J Comp Med. 1985 Jul;49(3):346-9.
Plasma progesterone levels on day 4 and day 8 postbreeding were measured for one hundred and eighty-four dairy cows. These two parameters (PPD4, PPD8), their absolute difference (PPDIFF) and their ratio (PPRATIO) were assessed for their ability to identify cows not conceiving, using the principles of sensitivity and specificity. PPD4 was significantly higher (p less than 0.10) and PPD8, PPDIFF and PPRATIO were significantly lower (p less than 0.01) in cows remaining open than in pregnant cows. Evaluating each parameter separately, PPDIFF greater than 3.00 units had the highest specificity, 85.7%, but a low sensitivity (27.0%). Combining two parameters using series interpretation to increase specificity resulted in the best combination of specificity (87%) and sensitivity (27%). Maximum specificity was 97% for PPD4 less than or equal to 1.00 units and PPD8 greater than 4.00 units, and also for PPD4 less than or equal to 1.00 units and PPDIFF greater than 3.00 units, but sensitivity was very low (7% and 10% respectively). Predictive values of the test results with the best specificity were evaluated; given the population pregnancy rate of 54%, none exceeded 50%, indicating that the plasma progesterone parameters were not very useful for identifying open dairy cows.
对184头奶牛在配种后第4天和第8天的血浆孕酮水平进行了测量。利用敏感性和特异性原则，评估了这两个参数（PPD4、PPD8）、它们的绝对差值（PPDIFF）以及它们的比值（PPRATIO）识别未受孕奶牛的能力。未受孕奶牛的PPD4显著更高（p小于0.10），而PPD8、PPDIFF和PPRATIO显著更低（p小于0.01）。单独评估每个参数时，PPDIFF大于3.00单位具有最高的特异性，为85.7%，但敏感性较低（27.0%）。使用串联解释组合两个参数以提高特异性，得到了特异性（87%）和敏感性（27%）的最佳组合。当PPD4小于或等于1.00单位且PPD8大于4.00单位时，以及当PPD4小于或等于1.00单位且PPDIFF大于3.00单位时，最大特异性为97%，但敏感性非常低（分别为7%和10%）。评估了具有最佳特异性的检测结果的预测值；考虑到群体妊娠率为54%，没有一个超过50%，这表明血浆孕酮参数对于识别未受孕的奶牛不是非常有用。
