Symons R G, Vining R F
Clin Chem. 1985 Aug;31(8):1342-8.
We evaluated the fluorescence polarization immunoassay for total thyroxin (T4) and thyroxin-uptake (T-U) in the Abbott "TDx" Analyzer. Between-assay precision was good when we did once-fortnightly calibration and assayed samples in singleton. Measured T4 concentration was decreased in hemolyzed samples with obvious red coloration and undetectable in severely hemolyzed samples. The T-U assay was unaffected by hemolysis. Unlike the triiodothyronine-uptake methods, the T-U assay utilizes labeled T4 and measures a variable related to serum thyroxin-binding capacity rather than the concentration of unoccupied binding sites in serum. The T4 and T-U values of 422 samples correlated highly with a T4 (in-house) radioimmunoassay and a commercial assay for thyroxin-binding globulin, respectively. The free thyroxin ratio (ratio of T4 to T-U, FTI) correlated highly with free T4 concentration as measured by T4-analog-tracer radioimmunoassay (fT4 analog RIA). FTI and fT4 values were discordant in late pregnancy (normal FTI and low fT4) and euthyroid sick patients (above-normal or normal FTI and low fT4), suggesting that the FTI gives fewer misleading results in these patients.
我们在雅培“TDx”分析仪上评估了总甲状腺素（T4）和甲状腺素摄取（T-U）的荧光偏振免疫测定法。当我们每两周进行一次校准并单独检测样本时，批间精密度良好。在明显呈红色的溶血样本中，测得的T4浓度降低，在严重溶血样本中无法检测到。T-U测定不受溶血影响。与三碘甲状腺原氨酸摄取方法不同，T-U测定使用标记的T4，并测量与血清甲状腺素结合能力相关的变量，而不是血清中未占据结合位点的浓度。422份样本的T4和T-U值分别与T4（内部）放射免疫测定法和甲状腺素结合球蛋白的商业测定法高度相关。游离甲状腺素比率（T4与T-U的比率，FTI）与通过T4类似物示踪放射免疫测定法（fT4类似物RIA）测得的游离T4浓度高度相关。在妊娠晚期（FTI正常而fT4低）和甲状腺功能正常的患病患者（FTI高于正常或正常而fT4低）中，FTI和fT4值不一致，这表明FTI在这些患者中产生误导性结果的情况较少。
