Classically, to perform a radioimmunoassay, a known quantity of an antigen is made radioactive, frequently by labeling it with gamma-radioactive isotopes of iodine, such as 125-I, or tritium[1] attached to tyrosine.

This value is then compared to a standardised calibration curve to work out the concentration of the unlabelled antigen in the patient serum sample.

The RIA would begin with the "cold" unlabeled antibody being allowed to interact and bind to the target molecule in solution.

[3] This method was developed by Solomon Berson and Rosalyn Sussman Yalow at the Veterans Administration Hospital in the Bronx, New York.

[6] In her acceptance speech, Dr. Yalow said, "The world cannot afford the loss of the talents of half its people if we are to solve the many problems which beset us.