Question

On what principle ELISA test is based?

Answer 1

Hint: The full form of ELISA is the enzyme-linked immunosorbent assay. It is a type of immunoassay that is used to quantify the level of a specific target in the sample, common samples used for the ELISA are serum, plasma, saliva, etc. It depends on the antibody in order to detect the specific antigen in the sample.

Complete answer:
- The ELISA test is performed in the multi-well plate, where the antigen is fixed in the middle, the specific arrangement helps to test the multiple samples at a time.
- There are four types of ELISA tests which include Direct, Indirect, Sandwich, and competitive, and every type has its own advantage and disadvantage.

> Direct ELISA:
- In this type the antigen is directly immobilized at the center of the plate and substrate is added
- Mainly it is used to find antibody affinity
- Advantage: This is a simple and easy method.
- Disadvantage: This is less specific as they are using only one antibody

> Indirect ELISA:
- It is similar to the indirect test as the antigen is immobilized and placed at the center, but in this, the amplification process is added.
- It is mainly used to find endogenous bacteria.
- Advantage: because of amplification, a secondary antibody is used
- Disadvantage: Because of the use of a secondary antibody, there is a chance of cross-reactivity.

> Sandwich ELISA:
- It is the most common type, in this antigen is a sandwich between the two antibodies.
- It is used to determine the analytical concentration in the given biological sample
- Advantage: It has the highest specificity and sensitivity
- Disadvantage: It is a very long and time taking protocol.

> Competitive ELISA:
- It is commonly used for a smaller molecule when the protein of interest is very small
- It helps to determine the concentration of small molecules and hormones.
- Advantage: It is used to quantify the smaller molecules.
- Disadvantage: It is not specific as it is using only one antibody.

Note: ELISA is usually done by evaluating the either presence of an antigen or antibody and it is a commonly used test for the HIV and a part for disease, it is also used to detect the allergies for food like peanuts, milk, eggs, etc.