The ELISA (enzyme-linked immunosorbent assay) is a biochemical test that is used as a diagnostic tool in biotechnology and medicine.
Direct ELISA
Direct ELISA is an enzyme linked immunosorbent assay used for the quantification and detection of a specific substance (analyte). The analyte can be an antibody or antigen. An antigen’s presence in the blood serum is found by the way it is attached to specific antibodies. These antibodies are usually linked with enzymes. The enzyme produces a signal or colour change in the substrate. This indicates the presence of disease-causing agents in the blood serum.
The signal intensity of direct ELISA is very weak. Also, it is less sensitive when compared to indirect ELISA.
Indirect ELISA
Indirect ELISA can be done using primary as well as secondary antibodies. These antibodies amplify the signals, and are thus stronger than the direct ELISA. Also, it is more sensitive than direct ELISA.
Difference between Direct and Indirect ELISA
Direct ELISA |
Indirect ELISA |
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Direct ELISA uses only one type of antibody. |
Indirect ELISA uses primary as well as secondary antibodies. |
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It is less time consuming than indirect ELISA. |
It takes a longer time to run. |
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Direct ELISA is less sensitive. |
It is more sensitive. |
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Signals are weak here. |
Indirect ELISA creates amplified signals. |
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There is no cross-reactivity between the secondary antibodies. |
The cross-reactivity between the secondary antibodies can create a false signal. |
Also Read: Antigens and Immunology
Frequently Asked Questions
What is sandwich ELISA?
It is also a type of ELISA that uses two antibodies. Here, the antigen is bound between two layers of antibodies. It is even more sensitive than indirect ELISA, and is used for the analysis of complex analytes.
What are the applications of ELISA?
ELISA is used to detect the presence of antigens and antibodies in a given sample. Thus, it plays a vital role in the medicinal field as well as in drug screening. Also, it is used in the food industry to detect the presence of any food allergens. It is also used to detect various disease outbreaks (malaria, zika virus, syphilis, etc.)
Extended Reading: ELISA Technique
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