Interrelations of the various mathematical approaches to radioimmunoassay.

Equations used for calculation of radioimmunoassay data are derived and compared. We show that the equation developed by Fernandez and Loeb is the most general of these. Those of Ekins et al., Hales and Randle, and Rodbard et al. are all derived here from this basic equation by neglecting certain of its terms. The logit-log plot of Rodbard et al. is a logarithmic transformation of the linear Hales-Randle equation. The basic equation, derived here solely from the mass-action law, approaches linearity under certain conditions without complex mathematical transformations of analyte concentrations or observable parameters. Applications are also presented.