Radioactive isotopes Radioactive isotopes can be incorporated into immunoassay reagents to produce a radioimmunoassay (RIA).Radioactivity emitted by bound okamoapaseatea7tandsngomao RIAs were some of the earliest immunoassays developed,but have fallen out of fav wich ELISA run on a microtit DNA reporters A newer approach to immunoassays involves combining real-time quantitative polymerase chain reaction(RT PCR)rea-imemmiiv PCR(CR)the label used in these assays is a DNA probe Fluorogenic reporters micarayar ofthat ofen mloy ugnic Fluorogenic reporters like phycoerythrin are used in a number of modern immun Electrochemiluminescent tags onse to electric cu an el Label-free immunoassays not rely on it do s of th eis an that can detect bindin between an unlabeled antibody and antigen measuring the change in resistance on an electrode as antigen binds to it. Classifications and formats Competitive,homogeneous immunoassays mogeneous d competes sample.the more labelled analyte gets competed off and hence the amount of labelled.unbound analyte is proportional to the amount of analyte in the sample. Competitive,heterogeneous immunoassays As in a competitive.ho os immunoassay unlabelled analyte in a sample co and the remaining labelled,bound analyte is measured