Huang C M, Zweig M
Clinical Pathology Department, Warren Grant Magnuson Clinical Center, Bethesda, MD 20892.
Clin Chem. 1989 Jan;35(1):125-6.
We evaluated the Kallestad "Quanticoat" cortisol RIA for direct (no extraction) measurement of urinary free cortisol, which requires no solvent extraction. An analytical-recovery study showed a linear regression of y (measured) = 0.65x (added) + 37.5 micrograms/L (Sy.x = 21.4 micrograms/L, r = 0.978, n = 48). Recovery appeared to vary with the urine used and with the concentrations of cortisol added. Within- and between-run CVs were less than or equal to 4.1% and less than or equal to 3.8%, respectively. Cross reactivities were low, except for prednisolone (20.5%). This no-extraction method gave higher values for urinary free cortisol than did either an RIA method involving extraction or an HPLC method. A comparison study with the HPLC (x) and with the method involving extraction (x') gave the following Deming-debiased regression equations: y = 1.60x + 68.8 (Sy.x = 34.4, n = 29) and y = 1.33x' + 0.69 (Sy.x = 40.3, n = 66), respectively. We conclude that the no-extraction method may give misleading results for patients' diagnosis or management if this cross reactivity is not taken into account.
我们评估了Kallestad“Quanticoat”皮质醇放射免疫分析方法，用于直接（无需萃取）测量尿游离皮质醇，该方法无需溶剂萃取。一项分析回收率研究显示，y（测量值）= 0.65x（添加值）+ 37.5微克/升的线性回归方程（Sy.x = 21.4微克/升，r = 0.978，n = 48）。回收率似乎随所用尿液以及添加的皮质醇浓度而变化。批内和批间变异系数分别小于或等于4.1%和小于或等于3.8%。除泼尼松龙（20.5%）外，交叉反应率较低。这种无需萃取的方法所测得的尿游离皮质醇值高于涉及萃取的放射免疫分析方法或高效液相色谱法。与高效液相色谱法（x）和涉及萃取的方法（x'）的比较研究得出以下Deming偏差校正回归方程：y = 1.60x + 68.8（Sy.x = 34.4，n = 29）和y = 1.33x' + 0.69（Sy.x = 40.3，n = 66）。我们得出结论，如果不考虑这种交叉反应性，这种无需萃取的方法可能会在患者诊断或治疗管理方面给出误导性结果。
