Porter W H, Haver V M, Bush B A
Clin Chem. 1984 Nov;30(11):1826-9.
Determination of digoxin by fluorescence polarization immunoassay (FPIA) with the Abbott "TDx" is significantly influenced by the concentration of total serum protein. Each 10 g/L increase in serum protein results in an 8% decrease in measured digoxin. Studies with [3H]digoxin confirmed that digoxin binds to the protein pellet during the trichloroacetic acid precipitation step before the immunoassay. Serum protein, or equal concentrations of albumin or gamma-globulin, exert an equivalent effect on the apparent digoxin value. Because the total protein concentration of the assay calibrators is low (50 g/L) compared with its reference interval in serum (60-80 g/L), results by FPIA may be expected to be low by an average of 16% (range, 8-24%). Digoxin results by FPIA will be most nearly accurate when the calibrators include a total protein concentration of about 70 g/L. Patients' specimens with abnormally high or low protein content will give falsely high or low results for digoxin.
采用雅培“TDx”荧光偏振免疫分析法（FPIA）测定地高辛时，血清总蛋白浓度会对结果产生显著影响。血清蛋白浓度每升高10 g/L，测得的地高辛浓度就会降低8%。用[3H]地高辛进行的研究证实，在地高辛免疫分析前的三氯乙酸沉淀步骤中，地高辛会与蛋白质沉淀结合。血清蛋白、等量的白蛋白或γ球蛋白对表观地高辛值的影响相同。由于分析校准品的总蛋白浓度（50 g/L）低于血清中的参考区间（60 - 80 g/L），预计FPIA法测得的结果平均会低16%（范围为8% - 24%）。当校准品的总蛋白浓度约为70 g/L时，FPIA法测定的地高辛结果最接近准确值。蛋白质含量异常高或低的患者样本，会使地高辛检测结果出现假高或假低的情况。
