[Problems with standardization of the radioimmunologic determination].

Radioimmunoassay is an analytical procedure in which a radioactive tracer acts as an indicator and a specific antibody acts as a reagent. The requirements which have to be met to guarantee the validity of the assay are the essential characteristics of each microanalytical procedure, namely the sensitivity, specificity, precision and accuracy. The optimization of the assay demands than a careful examination of these factors, which first depend on the properties of the reagents. The consistency of the results is based on the identity, as far as the immunoreactivity is concerned, between the substance to be assayed in the biological sample and the substance used as a standard to build up the calibration curve. The immunoreactivity of the tracer can instead be lower than that shown by the standard, although it must not be too different. The features of all the reagents are reviewed and discussed, mainly those of the antiserum which affect the specificity of the assay. The most diffuse RIA techniques are reviewed and divided in gross categories, according to the methods used for the separation of the free and antibody-bound hormone. The different steps of the analytical procedure are investigated, taking into consideration the most important parameters which affect the assay, mainly the time and temperature of the incubation step. The practical ease of the analysis is definitely an essential factor of choice, provided that it could be associated to reproducible and accurate results. A severe quality control of each reagent and of the assembled set must be carried out to assure the consistency of the analytical data. In the particular case of radioimmunoassay the quality control must be extended to all the steps of the assay both before and after the analytical procedure itself, in order to assure the maximal clinical validity of the diagnostic determination.