What is the Difference Between ELISA and Rapid Test

The main difference between ELISA and rapid test is that ELISA is time-consuming, whereas rapid test is fast in detecting antigens.

ELISA and rapid test are two tests that detect the presence of antigens in a sample. Both types of tests depend on the antigen-antibody interactions.    

Key Areas Covered

1. What is an ELISA
– Definition, Types, Function
2. What is a Rapid Test
– Definition, Process, Function
3. Similarities Between ELISA and Rapid Test
– Outline of Common Features
4. Difference Between ELISA and Rapid Test
– Comparison of Key Differences

Key Terms

ELISA, Rapid Test

What is an ELISA

ELISA (enzyme-linked immunosorbent assay) is a type of solid-phase enzyme immunoassay responsible for detecting specific proteins in biological samples with the help of primary antibodies. In this test, an enzymatic reaction helps to detect the bound primary antibodies. Here, the enzyme uses a chromogenic substrate to develop a color. Moreover, the solid phase used by the ELISA is mainly a microtiter plate. Also, there are three types of ELISA: direct ELISA, Indirect ELISA, and sandwich ELISA.

Figure 1: ELISA

Direct ELISA

In direct ELISA, coating the surface of a plate with the sample enables the enzyme-linked antibodies to bind with the specific protein on the plate. Then, adding the chromogenic substrate aids in detecting the protein-bound antibodies.

Indirect ELISA

Indirect ELISA involves the detection of a specific protein in a sample with a two-step binding process. Here, the first step is coating a plate with the sample and incubating it with a specific type of primary antibody. Then, the next step is incubating this plate with a secondary antibody, which binds to the primary antibody. Further, this secondary antibody has a link with an enzyme. Therefore, adding the chromogenic substrate aids in detecting the specific protein on the plate using color development.

Sandwich ELISA

The first step in the sandwich ELISA is to sandwich the specific protein to be detected from the sample between the primary and the secondary antibody. Here, the first process is to coat the plate with the primary antibody but not with the sample. Then, the next process is to incubate the sample with this plate. After that, the specific protein bound to the primary antibody can be detected with the help of a secondary antibody.

What is a Rapid Test

Rapid test is a rapid antigen detection test that directly detects the presence or absence of antigens in a sample. However, it is not used to detect antibodies and nucleic acids. Importantly, it gives results within 5 to 30 minutes. Also, it requires minimal training infrastructure. Additionally, it is more cost-effective than ELISA testing. Among other tests, it is important for the qualitative detection of infections in blood samples, plasma, or serum. Similar to ELISA, rapid tests use monoclonal or polyclonal antibodies to detect elevated levels of infections.

Figure 2: Rapid Test

Moreover, in rapid tests, antibodies directed against the target antigen are fixed in an indicator line. Also, they bear a visualization marker, generally a dye. When the sample is added, the target antigen binds to the specific antibody to give the color.

Similarities Between ELISA and Rapid Test

• ELISA and rapid test are two tests that detect the presence of antigens in samples.
• They depend on antigen-antibody interactions.
• Both use different types of antibodies to detect antigens.

Difference Between ELISA and Rapid Test

Definition

ELISA refers to an assay commonly used to measure antibodies, antigens, proteins, and glycoproteins in a sample. In contrast, a rapid test refers to a test done using a small medical device that tests whether or not there is a particular substance, gene, etc., in a sample.

Type of Detection

ELISA detects antigens, antibodies, and nucleic acids, while rapid test detects antigens.

Time

ELISA test is not fast, while the rapid test is fast.

Apparatus

ELISA uses microplate readers and plate washers, pipettes, dispensers, incubator/shakers, and centrifuges, while rapid test uses a small medical device.

Training

ELISA requires training to proceed with the test, while rapid test requires minimal training.

Cost

ELISA is costlier than a rapid test.

Conclusion

In brief, ELISA and rapid test are two tests that detect the presence of antigens in samples. Both use antigen-antibody interactions for this purpose. ELISA is the use of antibodies to detect the presence of proteins and nucleic acids in a sample. It is not a fast test, and it requires training to proceed with the test. Also, it is not cost-effective. In comparison, a rapid test detects antigens within a few minutes. Therefore, it is a fast test. Also, it requires minimal training and has a low cost. Hence, the main difference between ELISA and rapid tests is the advantages of the rapid test.

References:

1. Al-Matary AM, Al Gashaa FAS. Comparison of different rapid screening tests and ELISA for HBV, HCV, and HIV among healthy blood donors and recipients at Jibla University Hospital Yemen. J Med Life. 2022 Nov;15(11):1403-1408. doi: 10.25122/jml-2022-0051. PMID: 36567845; PMCID: PMC9762378.

Image Courtesy:

1. “ELISA TMB” By Ajpolino. – Own work (CC0) via Commons Wikimedia
2. “COVID-19-Antigen-with-Influenza-A-B-Rapid-Antigen-Combo” By Amrithraj – Own Work (CC-BY SA 4.0) via Commons Wikimedia