Comparison of four methods to assess colostral IgG concentration in dairy cows
Comparison of four methods to assess colostral IgG concentration in dairy cows
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DOI：
10.2460/javma.233.5.761
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发表时间：
2008-09-01
影响因子：
1.9
通讯作者：
Steevens, Barry J.
中科院分区：
文献类型：
--
作者：
Chigerwe, Munashe;Tyler, Jeff W.;Steevens, Barry J.
目的：确定4种方法测定奶牛初乳免疫球蛋白浓度的敏感性和特异性，并确定每种方法的最佳切入点。设计-横断面研究。动物-160头荷斯坦奶牛。Procedures-171份分娩后2小时内采集的合成初乳样本用于研究。测定初乳免疫球蛋白浓度的方法包括第一次挤奶时的重量、2个比重计和电子折射仪，并与放射免疫扩散法测定的初乳免疫球蛋白浓度进行比较。对于每一种方法，计算了检测初乳免疫球蛋白浓度和50g/L的敏感性和特异性，并选择了每种检测的最佳界点，以最大限度地提高敏感性和特异性。结果：在每种方法的最佳切割点，首次挤奶对重量的敏感性(0.42)显著低于其他3种方法(比重计1、0、75、比重计2、0.76、折光仪0.75)的敏感性，但其他3种方法之间的敏感性无显著差异。所有4种方法在最佳切点的特异性都相似。结论和临床相关性-结果表明，使用比重计或电子折射计是一种可以接受的方法，用于筛选低浓度的初乳；然而，制造商定义的这两种比重计的标尺高估了初乳中的免疫球蛋白浓度。使用第一次挤奶的重量作为筛选试验来鉴定免疫球蛋白浓度不足的牛初乳是不合理的，因为敏感性较低。
Objective-To determine sensitivity and specificity of 4 methods to assess colostral IgG concentration in dairy cows and determine the optimal cutpoint for each method.Design-Cross-sectional study. Animals-160 Holstein dairy cows.Procedures-171 composite colostrum samples collected within 2 hours after parturition were Used in the study. Test methods used to estimate colostral IgG concentration consisted of weight of the first milking, 2 hydrometers, and an electronic refractometer.Results of the test methods were compared with colostral IgG concentration determined by means of radial immunodiffusion. For each method, sensitivity and specificity for detecting colostral IgG concentration < 50 g/L were calculated across a range of potential cutpoints, and the optimal cutpoint for each test was selected to maximize sensitivity and specificity. Results-At the optimal cutpoint for each method, sensitivity for weight of the first milking (0.42) was significantly lower than sensitivity for each of the other 3 methods (hydrometer 1, 0,75, hydrometer 2, 0.76, refractometer, 0.75), but no significant differences were identified among the other 3 methods with regard to sensitivity. Specificities at the optimal cutpoint were similar for all 4 methods.Conclusions and Clinical Relevance-Results suggested that use of either hydrometer or the electronic refractometer was an acceptable method of screening colostrum for low IgG concentration; however, the manufacturer-defined scale for both hydrometers overestimated colostral IgG concentration. Use of weight of the first milking as a screening test to identify bovine colostrum with inadequate IgG concentration could not be justified because of the low sensitivity.