what is a radioimmunoassay? How do they work?


The google answers are so confusing 😅

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Radioimmunoassay (RIA) is a scientific test that helps doctors and scientists measure very small amounts of things called “molecules” in our bodies.

Imagine that molecules are like tiny pieces of Lego that make up everything in our bodies, like muscles, bones, and even blood. Scientists want to measure how many of these Lego pieces are in our blood to check if we’re healthy or if we have any problems.

To do this, they use a special kind of Lego piece that has a tiny bit of radiation attached to it. This Lego piece is called a “radioactive tracer.”

Next, scientists put some of our blood into a test tube with some Lego pieces that stick to the molecule they want to measure. These Lego pieces are called “antibodies.”

The antibodies and radioactive tracer Lego pieces will compete to attach to the molecule being measured. After a while, scientists measure how much radiation is in the test tube. The more radiation there is, the less of the molecule being measured is in our blood.

So, in short, RIA is a test that uses special Lego pieces with radiation to measure how many molecules of a certain type are in our blood.

You have a solution with a molecule of interest; let’s call that the MoI. The solution could be something like blood from a patient.

We’ll take a test tube or microplate well, and coat it with something that our MoI will stick to. Then we add the blood, allow it to react for a moment, and wash it out of the tube. Our MoI is still stuck to the coating, but everything else from the blood sample is gone.

Then we add a second molecule that binds to our MoI (and not to the original coating). This molecule also contains a radioactive part. Again, we allow it to react for a while, then wash out the tube. Now all that’s left in the tube is coating, MoI bound to it, and radioactive second molecule bound to MoI.

We can pass the tube through a radioactivity-measuring device, and the readout is proportional to how much MoI was present in the original blood sample. We’d need a second tube where we added a known amount of MoI to really quantify the concentration in unknown samples.