Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853.
Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853.
J Dairy Sci. 2018 Feb;101(2):1334-1343. doi: 10.3168/jds.2017-13779. Epub 2017 Dec 14.
The objective of this study was to assess an optimized ion-selective electrode Ca-module prototype as a potential cow-side device for ionized Ca (iCa) measurements in bovine blood. A linearity experiment showed no deviation from linearity over a range of iCa concentrations compared with a commercial point-of-care (POC) device commonly used in the field (POC; VetScan i-STAT, Abaxis North America, Union City, CA) and a laboratory gold standard benchtop blood-gas analyzer [reference analyzer (RA); ABL-800 FLEX, Radiometer Medical, Copenhagen, Denmark]. Coefficient of variation on 3 samples with high, within-range, and low iCa concentrations ranged from 1.0 to 3.9% for the prototype. A follow-up validation experiment was performed, in which our objectives were to (1) assess the performance of the prototype cow-side against the POC (farm gold-standard) using fresh non-anticoagulated whole-blood samples; (2) assess the performance of the prototype and the POC against the RA in a diagnostic laboratory using blood collected in a heparin-balanced syringe; and (3) assess the agreement of the prototype and POC on-farm (fresh non-anticoagulated whole blood) against the RA on heparin-balanced blood. Finally, sensitivity and specificity of the results obtained by the prototype and the POC cow-side compared with the results obtained by the laboratory RA using 3 different iCa cut points for classification of subclinical hypocalcemia were calculated. A total of 101 periparturient Holstein cows from 3 dairy farms in New York State were used for the second experiment. Ionized Ca results from the prototype cow-side were, on average, 0.06 mmol/L higher than the POC. With heparin-balanced samples under laboratory conditions, the prototype and POC measured an average 0.04 mmol/L higher and lower, respectively, compared with the RA. Results from the prototype and POC cow-side were 0.01 mmol/L higher and 0.05 mmol/L lower, respectively, compared with results from the laboratory RA on heparinized blood. Sensitivity and specificity for the prototype and the POC under farm conditions at 3 potential subclinical hypocalcemia cut points were 100 and ≥93.5%, respectively. This novel ion-selective electrode Ca-module could become a rapid low-cost tool for assessing iCa cow-side, while qualitatively allowing classification of subclinical hypocalcemia on-farm.
本研究旨在评估优化后的离子选择性电极 Ca 模块原型作为一种潜在的牛场设备，用于测量牛血液中的离子化钙 (iCa)。与现场常用的商业即时检测 (POC) 设备（POC；VetScan i-STAT，Abaxis North America，Union City，CA）和实验室金标准台式血气分析仪相比，线性实验显示该原型在 iCa 浓度范围内没有偏离线性 [参考分析仪 (RA)；ABL-800 FLEX，Radiometer Medical，Copenhagen，Denmark]。在高、中、低 iCa 浓度的 3 个样本上，变异系数为 1.0%至 3.9%。随后进行了验证实验，目的是：（1）使用新鲜非抗凝全血样本评估原型牛场设备与 POC（农场金标准）的性能；（2）在诊断实验室中，使用肝素平衡注射器采集的血液评估原型和 POC 与 RA 的性能；（3）评估原型和 POC 在牛场（新鲜非抗凝全血）与 RA 在肝素平衡血液上的一致性。最后，计算原型和 POC 牛场设备与实验室 RA 基于 3 种不同 iCa 切点用于亚临床低钙血症分类的结果之间的灵敏度和特异性。第二个实验共使用了来自纽约州 3 个奶牛场的 101 头围产期荷斯坦奶牛。原型牛场的 iCa 结果平均比 POC 高 0.06mmol/L。在实验室条件下使用肝素平衡样本时，原型和 POC 分别比 RA 高 0.04mmol/L 和低 0.04mmol/L。与肝素化血液的实验室 RA 结果相比，原型和 POC 牛场设备的结果分别高 0.01mmol/L 和低 0.05mmol/L。在 3 个潜在亚临床低钙血症切点下，原型和 POC 在农场条件下的灵敏度和特异性分别为 100%和≥93.5%。这种新型离子选择性电极 Ca 模块可能成为一种快速、低成本的 iCa 牛场评估工具，同时能够定性地在农场进行亚临床低钙血症的分类。
