What is the Difference Between Radioimmunoassay and Immunoradiometric Assay?
🆚 Go to Comparative Table 🆚Radioimmunoassay (RIA) and Immunoradiometric Assay (IRMA) are both immunoassays that use radiolabeled components to detect and quantify specific macromolecules in a sample. However, there are some key differences between the two methods:
- Reaction: In RIA, the sample or compound to be measured displaces another antigen gradually over some period, while in IRMA, the sample or compound combines immediately with the radiolabeled antibodies.
- Sensitivity: IRMA is known for its improved sensitivity compared to conventional RIA. For example, when measuring serum prostatic acid phosphatase, IRMA showed excellent precision over a much wider working range (0.25-1000 micrograms/l) than RIA.
- Assay Time: IRMA can be completed in a shorter time (5 hours) compared to RIA, which requires 3 days for completion.
- Comparison of Results: When measuring prostatic acid phosphatase in serum, IRMA and RIA results were highly correlated (r = 0.97), but IRMA results were generally lower than those obtained by RIA.
In summary, while both RIA and IRMA use radiolabeled components to detect and quantify specific macromolecules in a sample, the key differences lie in the reaction mechanism, sensitivity, assay time, and comparison of results.
Comparative Table: Radioimmunoassay vs Immunoradiometric Assay
Here is a table comparing the key differences between Radioimmunoassay (RIA) and Immunoradiometric Assay (IRMA):
Feature | Radioimmunoassay (RIA) | Immunoradiometric Assay (IRMA) |
---|---|---|
Description | An immunoassay that uses radioactive elements to detect the amount of antigen in a sample. | An immunoassay that uses radiolabeled antibodies to determine antigen levels in a sample. |
Radioactive Elements | Radioactive antibodies are used. | Radioisotopes are used to label antibodies. |
Competitive Binding | A radioactive antigen competes against a non-radioactive antigen for a constant amount of antibody. | The sample or compound immediately combines with the radiolabeled antibodies. |
Assay Procedure | The sample or compound to be measured is combined with a radioactive antigen before the combination. | The sample or compound is combined immediately with the radiolabeled antibodies. |
Precision | Precision varies depending on the specific assay conditions. | IRMA shows excellent precision over a wider working range than RIA. |
Completion Time | RIA typically requires more time, around 3 days. | IRMA can be completed in less time, typically 5 hours. |
Sensitivity | RIA is very specific and highly sensitive. | IRMA generally has a higher sensitivity. |
Correlation with RIA | In some cases, such as measuring serum prostatic acid phosphatase, IRMA results may be generally lower than those obtained by RIA, but the two methods correlate well. |
In summary, the main difference between RIA and IRMA is that RIA uses radioactive antibodies and relies on competitive binding, while IRMA uses radiolabeled antibodies and has a more immediate combination with the sample or compound. IRMA tends to have better precision, sensitivity, and faster completion time compared to RIA.
- Radioisotope vs Isotope
- RIA vs ELISA
- Radioactive Contamination vs Irradiation
- Radiation vs Irradiation
- Radioactivity vs Radiation
- Immunofluorescence vs Immunohistochemistry
- Immunoprecipitation vs Coimmunoprecipitation
- Immunocytochemistry vs Immunohistochemistry
- Colorimetric vs Fluorometric Assay
- Radioactive vs Nonradioactive Probes
- Atomic Absorption vs Atomic Emission
- Radiology vs Radiography
- Stable Isotopes vs Radioisotopes
- Relative Dating vs Radiometric Dating
- In Situ Hybridization vs Immunohistochemistry
- Bioassay vs Chemical Assay
- ELISA vs Rapid Test
- Direct vs Indirect Immunofluorescence
- Serology vs Immunology