利用概率单位法估算EC_(50)的研究

Estimation of Probit Methods on EC_(50)

以两组典型毒性数据为例,综合比较了5种常见概率单位模型计算程序在EC50估算上的差异,并在此基础上比较了3种不同置信区间的估算方法.在对照组受抑制率为零时,5种方法的参数估算结果一致;当对照组受抑制率不为零时,将对照组数据纳入整个计算过程的方法可以给出可靠的参数估算结果.3种不同置信区间估算方法的比较表明:在毒性数据分布对称性良好的情况下,基于Delta函数与Fieller定理的方法给出的结果相近,但后者可以在更广泛的情况下给出置信区间;相比而言,基于bootstrap重抽样的非参数方法获得的置信区间较窄,表现出更好的灵敏度.

The differences of EC50 estimated by five computer programs which were widely used to estimate the parameters of probit model,have been comprehensively compared using two sets of typical toxicological data.Addtionally,three kinds of estimation on confidence interval have been also studied.When the inhibited ratio of control group was zero,parameters and EC50 obtained from five programs were consistent well.If control ratio was larger than zero,only the program,which took the control dataset into parameter estimation,could give the reliable results.The confidence interval obtained from the three kinds of estimation has been showed a closely results,which were based on Delta function and Fieller’s theorem,and the distribution of dataset was well symmetrical;The confidence interval estimated by Fieller＇s theorem could give better results in generalization.In contrast,the confidence interval obtained from nonparametric method based on the bootstrap resampling technique is much narrower,accordingly,the confidence interval showed better sensitivity.