Elizabeth Howe, age 16, of Kalispell, Mont., for her question:

CAN YOU EXPLAIN RADIOIMMUNOASSY?

Radioimmunoassy is a technique used in medicine and biochemistry for determining or expressing the quantity of very small amounts of biological material such as enzymes, hormones, steroids and vitamins that can be found in saliva, blood, urine and other body fluids.

An American doctor named Solomon Berson and an America medical researcher named Rosalyn Yalow developed radioimmunoassay in the 1950s. Yalow in 1977 went on to receive the Nobel Prize in physiology and medicine for this great find.

A radioimmunoassay, or RIA as it is called, needs three things: a radioactively labeled preparation of the substance to be measured, an antibody to this material and a biological fluid containing an unknown amount of the material.

RIA is a useful research procedure used in hospitals to help diagnose diabetes, thyroid disorders, hypertension and other diseases.