Radioimmunoassay (RIA) is a very sensitive method that measures the presence of an antigen. Minute concentrations of any biological substance (for which a specific antibody exists) can be measured with this method. RIA has been the first immunoassay technique developed to analyze nanomolar and picomolar concentrations of hormones in biological fluids. Despite its extreme sensitivity and specificity, the RIA techniques remains the least expensive method to measure antigen concentrations.
Although radioimmunoassay is an old technique, it is still a widely used immunoassay technique, and continues to offer distinct advantages in terms of simplicity and especially sensitivity.More information about radioimmunoassays (RIA)