Radioimmunoassay (RIA) is an in vitro technique introduced in 1960 by Benson and Yalow to measure hormone levels in blood using antibodies. It involves the competitive binding of a radiolabeled antigen to antibodies. RIA is extremely sensitive and specific, requiring specialized equipment, but it remains one of the least expensive methods to perform such measurements, though it requires special precautions and licensing due to its use of radioactive substances. RIA is used to assay drugs, vitamins, and hormones like insulin, growth hormone, and thyroxin.

1. Dr. P. Saranraj
Head
Department of Microbiology
Sacred Heart College (Autonomous)
Tirupattur – 635 601
Tamil Nadu, India
Mobile: +91-9994146964; E.mail:
RADIO IMMUNOASSAY
(RIA)

2. RADIOIMMUNOASSAY (RIA)
 Radioimmunoassay (RIA) is an in
vitro Immunoassay technique used to
measure antigen concentrations
(hormone levels in blood) by use
of antibodies.
 In 1960, S. A Benson and Rosalyn Sussman
Yalow introduced RIA to determine levels of
Insulin – Anti-insulin complexes in Diabetics.
 In 1977, some years after Benson’s death, the
significance of the technique was acknowledged
by the award of a Nobel Prize to Yalow.
 The RIA involves the competitive binding of a
radiolabelled antigen to a high affinity

3. Advantages
 The RIA technique is
extremely sensitive and specific, requiring
specialized equipment.
 RIA remains among the least expensive
methods to perform such measurements.
Disadvantages
 The RIA requires special precautions and
licensing, since radioactive substances are
used.

5. Applications of RIA
 Used in the assay Drugs like Digitoxin,
Morphin, Barbifurate and Amphetonine.
 Analysis of Vitamins like Riboflavin and Folic
acid.
 Analysis of Hormones like Aldosterone, Insulin,
Growth hormone and Thyroxin.