RIA
Definition
Radioimmunoassay. Berson and Yalow, 1959. Heterogeneous, competitive, radioisotope label (most often 125-I). Highest sensitivity historically, now displaced in most Indian labs by ELISA and LC-MS/MS because of radioactive-waste handling.
- Full name
- Radioimmunoassay
- Origin
- Berson and Yalow, 1959
- Label
- Radioisotope, most often iodine-125
- Assay format
- Heterogeneous, competitive binding
- Current status
- Displaced by ELISA and LC-MS/MS in most Indian labs
Common questions
Why has RIA fallen out of favour in most forensic and clinical labs?+
Radioisotope use requires licensed handling, storage and disposal of radioactive waste under atomic energy regulations, which raises cost and compliance burden, so labs have largely shifted to ELISA and LC-MS/MS, which avoid radioactive material while offering comparable or better throughput.
Is RIA still used anywhere despite these drawbacks?+
Yes, in a shrinking number of specialised research and reference laboratories where its high sensitivity for particular analytes is still valued, though it is no longer the routine screening method in most forensic toxicology workflows.
Related terms
- Antibody
- An immunoglobulin (typically IgG) raised to bind a specific antigen. Source decides specificity: polyclonal antibodies recognise many epitopes, monoclonal antibodies recognise one.
- Antigen
- A molecule recognised by the adaptive immune system through specific binding to an antibody or T-cell receptor. Defined by immunogenicity (capacity to...
- Competitive vs Non-Competitive Format
- Competitive: labelled antigen and sample antigen compete for a limited number of antibody sites; signal is inversely proportional to analyte. Non-competitive (sandwich):...
- ELISA
- Enzyme-Linked Immunosorbent Assay. Heterogeneous, plate-based, enzyme label (HRP, alkaline phosphatase), colour or chemiluminescent readout. Four standard formats: direct, indirect, sandwich, competitive.
- Epitope and Hapten
- Epitope is the small surface patch on an antigen the antibody actually binds. A hapten is a small molecule (most drugs of...
- Homogeneous vs Heterogeneous
- Homogeneous assays (EMIT, FPIA) need no wash step, so they run fast on clinical analysers. Heterogeneous assays (ELISA, RIA) require a wash...
- Label
- The reporter coupled to either the antigen or the antibody so the binding event becomes measurable. Three families dominate: radioisotopes (RIA), enzymes...
- Lateral-Flow Immunoassay
- A point-of-care competitive immunochromatographic format on a nitrocellulose strip. In the absence of drug, colloidal gold-labelled antibody is captured at a test...