Gettys T W, Burrows P M, Henricks D M
Am J Physiol. 1986 Sep;251(3 Pt 1):E357-61. doi: 10.1152/ajpendo.1986.251.3.E357.
Software packages for radioimmunoassay calibration assume that expected counting rate is a function of ligand dose. Previous studies have indicated that variances of counting rate are also related to dose, but the structure of individual assays does not permit precise estimation of counting rate variances at individual doses. The method described here uses results from an accumulation of assays to characterize the relationship between mean and variance of counting rate, thus providing a variance weighting function for the calibration. Analysis of 140 cortisol assays, all with two replicates of each of 50 sources (9 standard doses, 3 quality control preps, and 38 unknowns), led to an asymmetric rising ogive relating variances to means of counting rates. A rectangular hyperbola provided an adequate characterization of this relationship in an accumulation of 21 testosterone assays. Relationships between mean and variance of counting rate in 19 growth hormone assays and 7 triiodothyronine assays were characterized by a straight line and a rising exponential curve, respectively. Calibration curves, such as the commonly adopted logistic ogive in relation to log dose, are fitted by weighted least squares to observed counts directly using empirical weights proportional to the reciprocal of estimated counting variance. The advantage of this method is that all observations contribute to the calibration in accordance with their merit.
放射免疫分析校准软件包假定预期计数率是配体剂量的函数。先前的研究表明，计数率的方差也与剂量有关，但单个分析的结构不允许精确估计各个剂量下的计数率方差。本文所述方法利用一系列分析的结果来表征计数率均值与方差之间的关系，从而为校准提供方差加权函数。对140次皮质醇分析进行分析，所有分析对50个来源中的每一个都进行了两次重复（9个标准剂量、3个质量控制制剂和38个未知样本），得出了一个将方差与计数率均值相关联的不对称上升S形曲线。在21次睾酮分析的累积中，一条矩形双曲线充分表征了这种关系。19次生长激素分析和7次三碘甲状腺原氨酸分析中计数率均值与方差之间的关系分别由一条直线和一条上升指数曲线表征。校准曲线，如与对数剂量相关的常用逻辑S形曲线，通过加权最小二乘法直接使用与估计计数方差的倒数成比例的经验权重拟合到观测计数上。该方法的优点是所有观测值都根据其价值对校准有所贡献。
