What’s In Your Blood?

It’s a nuclear medicine technique that you may not even have heard of before. Radioimmunoassay or (RIA) is a diagnostic procedure in hospital labs that measures biological material in your body through a process involving radioisotopes.

“RIA determines the levels of specific chemistries,” according to Jenny Ryan, science communications specialist, Canadian Blood Services. “It’s usually used in steroidal chemistry, like fertility hormones, vitamins, steroid and some cancer diagnosis.”

Copyright: Jarun Ontakrai

RIA is able to analyze large, complex molecules that can otherwise be difficult to assess. Viruses, peptic ulcers, leukemia and even insulin levels can all be measured using RIA.

The procedure was first developed in the late 1950s by scientists Rosalyn Yalow and Solomon Berson. Their discovery of what happens inside the human body earned Yalow the Nobel Prize in Physiology or Medicine in 1977.

RIA requires a radioactive isotope, antibodies, also known as immunoglobulins and blood from a patient. The hormone being measured is tagged with a radioactive isotope. This solution is then mixed with these antibodies, also known as proteins. The radioactive isotope and the antibodies chemically combine.

The next step is to add patient blood. This blood sample contains an unknown quantity of the hormone being measured. As the blood is introduced, antibodies move away from the isotopes and pair with the naturally occurring hormones. Once all the antibodies have moved away and paired up with the hormones in the blood, researchers then separate out all the hormone-antibody pairs (both the radioactive and the nonradioactive ones) and measure the radioactivity of the mixture.

The difference in the radioactivity of the mixture is called an assay or a measure and it indicates how much natural hormone was contained in the blood.

For example, if insulin is being measured radioisotope-tagged insulin is mixed with antibodies and then the blood sample from the patient is added. The insulin contained in the blood displaces some of the tagged insulin. The free-tagged insulin is then measured with isotope detectors and the patient’s insulin level is calculated.”

RIA testing is an important step in early and accurate diagnosis including colon cancer. The second most common cancer in Canada, and increasing, colorectal cancer, affects nearly 30,000 Canadians annually and nearly one million cases are confirmed every year across the global cancer community. The key to survival is early detection.

Radioimmunoassay; the nuclear connection to disease diagnosis.