Midgley J E, Winton M R, Wilkins T A
Clinical Reagents Research and Development Department, Amersham International plc, Amersham, Buckinghamshire, UK.
Clin Chim Acta. 1987 Jul 30;167(1):67-79. doi: 10.1016/0009-8981(87)90087-8.
We studied the effect of adding purified human albumin to sera on free thyroxine (FT4) values obtained with Amerlex radioimmunoassays. Apparent FT4 values increased with progressive addition of albumin in vitro. The effect was smallest with low and greatest with high initial FT4 concentrations, which were also linearly correlated with the incremental increase in FT4 values per g/l albumin added. Wide variations in either endogenous thyroxine binding globulin (TBG) or albumin concentrations in patient serum had little effect on the rate of increase in FT4 values when albumin was added in vitro. From Mass Action theory, calculations of the binding affinity of the endogenous albumin for the analog (2.1 X 10(5) l/mol) gave values nearly half that of the added albumin (3.94 X 10(5) l/mol). Distortions in Amerlex FT4 values caused by adding albumin in vitro may exaggerate its importance as a tracer binder and such results may be unrepresentative of patient samples.
我们研究了在血清中添加纯化人白蛋白对使用Amerlex放射免疫分析法获得的游离甲状腺素（FT4）值的影响。在体外，随着白蛋白的逐步添加，表观FT4值升高。初始FT4浓度低时该效应最小，而初始FT4浓度高时该效应最大，且初始FT4浓度与每克/升添加白蛋白时FT4值的增量增加也呈线性相关。当在体外添加白蛋白时，患者血清中内源性甲状腺素结合球蛋白（TBG）或白蛋白浓度的广泛变化对FT4值的增加速率影响很小。根据质量作用理论，计算得出内源性白蛋白对类似物的结合亲和力（2.1×10⁵升/摩尔），其值几乎是添加白蛋白（3.94×10⁵升/摩尔）的一半。体外添加白蛋白导致的Amerlex FT4值偏差可能会夸大其作为示踪剂结合物的重要性，并且这样的结果可能无法代表患者样本。
