Solter P F, Farner S
Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Illinois, Urbana 61802, USA.
J Vet Diagn Invest. 2000 Jan;12(1):51-6. doi: 10.1177/104063870001200109.
The purpose of this study was to compare 2 different nonradioactive assay methods with a conventional radioimmunoassay (RIA) measuring the concentration of serum thyroxine (T4) in horses. Serum was obtained from 85 adult standardbred horses. The T4 concentration of each sample was analyzed by RIA, chemiluminescent enzyme immunoassay (CEI), and homogeneous enzyme immunoassay (HEI). The correlation between the HEI method and RIA method was significantly greater (r = 0.89) than the correlation between the CEI and the reference method (r = 0.53). In addition, the precision of the HEI method was significantly greater than the CEI method; within-run percentage coefficients of variation were 4.5% and 15.9%, respectively, at mean T4 concentrations of 19-20 nmol/liter. On the basis of these findings, the HEI method was evaluated further. Both between-run precision and linearity were deemed adequate upon dilution by the HEI method. In addition, recovery of L-thyroxine added to equine serum was linear over 6 concentrations tested and averaged 79.6% with a manufacturer recommended data correction factor. An in-house correction factor was calculated by linear regression analysis of the RIA and HEI results from the original equine serum samples. Use of this correction factor improved the average recovery to 94.2% while maintaining excellent linearity (r2 = 0.9978). Although both nonradioactive methods of T4 analysis could likely substitute for the RIA reference method, the HEI method had the highest correlation and precision. The HEI technique also yielded adequately accurate results after correction of the data with an appropriate correction factor. Individually derived in-house correction factors may improve the accuracy of the HEI method to a greater extent than manufacturer suggested correction factors.
本研究的目的是将两种不同的非放射性检测方法与传统放射免疫分析法（RIA）进行比较，以测定马血清甲状腺素（T4）的浓度。从85匹成年标准赛马中采集血清。通过RIA、化学发光酶免疫分析法（CEI）和均相酶免疫分析法（HEI）分析每个样本的T4浓度。HEI法与RIA法之间的相关性（r = 0.89）显著高于CEI法与参考方法之间的相关性（r = 0.53）。此外，HEI法的精密度显著高于CEI法；在平均T4浓度为19 - 20 nmol/升时，批内变异系数百分比分别为4.5%和15.9%。基于这些发现，对HEI法进行了进一步评估。HEI法稀释后的批间精密度和线性均被认为是足够的。此外，添加到马血清中的L - 甲状腺素在6个测试浓度范围内的回收率呈线性，使用制造商推荐的数据校正因子时平均回收率为79.6%。通过对原始马血清样本的RIA和HEI结果进行线性回归分析，计算出内部校正因子。使用该校正因子可将平均回收率提高到94.2%，同时保持良好的线性（r2 = 0.9978）。虽然两种T4分析的非放射性方法都可能替代RIA参考方法，但HEI法具有最高的相关性和精密度。在用适当的校正因子对数据进行校正后，HEI技术也能产生足够准确的结果。与制造商建议的校正因子相比，单独得出的内部校正因子可能在更大程度上提高HEI法的准确性。
