Specific radioactivity of radioimmunoassay tracer determined by self-displacement: a re-evaluation

An error was discovered in the method of self-displacement commonly used for determining the specific radioactivity of labelling tracer antigen used in radioimmunoassay; viz. that the calculation does not take into account the mass of labelled antigen present in the mixture containing unlabelled antigen standard. A simple graphical plot is described to obviate this error so that the correct value for the specific radioactivity of a radioimmunoassay tracer can be reliably estimated