Difference between Antibody and Antigen Test

Immunoassays are a common type of bioanalysis because they utilise an antibody or an antigen to detect the presence of a target molecule in a biological sample. It is a sensitive biochemical assay for determining analyte presence or concentration. It is still a vital resource for doctors to use when dealing with infectious illnesses. Antibodies are used in these tests as an analytical reagent.

The immunoassay was developed by Berson and Yalow in 1959; in 1977, they were awarded the Nobel Prize in Medicine for their pioneering work on the radioimmunoassay technology. In the years following, immunoassays saw significant development. They were one of the century's most important technical advances in healthcare and the biological sciences.

What is Antibody Test?

Immunoglobulins, also known as gamma globulin proteins, are the building blocks of antibodies. Vertebrate blood and other bodily fluids include antibodies. They aid vertebrate immune systems in recognising and eliminating pathogens. This is why detecting antibodies in the blood is what an antibody test does.

The human body naturally generates antibodies for self-defense, however vaccination may be used to artificially increase antibody production. Testing for certain antibodies in the blood can reveal whether or not a person has been exposed to a particular virus or infection. The test only reveals whether or not the subject was previously infected, not whether or not they are now sick. A previous infection with SARS-CoV-2, for instance, is evidenced by a positive result for COVID-19 antibodies.

What is Antigen Test?

The presence of a specific viral antigen can be used as a quick diagnostic test to determine whether or not a person is currently infected with a virus. Clinical, emergency room, and central laboratory settings all employ antigen detection technologies to provide quick diagnoses. The diagnosis of infectious disorders, including COVID-19, may be made more quickly and affordably with the use of antigen testing.

Antigen tests have been used for quite some time to detect infectious pathogens that are too dangerous, too sluggish, or too difficult to culture. Specific binding of an antigen (protein or glycoprotein) to an antibody is the cornerstone of antigen detection tests. While antigen tests are less expensive than molecular approaches, they are not always as sensitive. Low sensitivity means they frequently provide negative findings when they should return positive ones.

Differences: Antibody and Antigen Test

The following table highlights the major differences between Antibody and Antigen Tests −


Antibody Test

Antigen Test


Antibodies (or immunoglobulin) are an element of the immune system that helps keep harmful germs and viruses out of the body.

Immune cells create them in reaction to antigens, or foreign substances. The immune system creates an antibody specific to the offending pathogen or antigen.

Antigens are defined as "foreign antigens" that can provoke an immunological response.


Testing for antibodies in the blood or serum can reveal whether or not a person has been exposed to a disease. In order to do this, they test for the existence of a host reaction to the virus.

Although they cannot confirm whether or not a someone now has the illness, they can reveal whether or not that person has been infected with the virus in the past.

However, if a person is actively infected with a disease, they will get positive results from an antigen test, which is a quick diagnostic test that identifies the presence of a specific viral antigen.


The sensitivity of the most common antibody test, known as an Enzyme-linked immunosorbent assay (ELISA), is 95%.

The enzyme-linked immunosorbent assay (ELISA) can be used to identify and measure antigens, antibodies, and other substances.

Antigen tests, on the other hand, can reveal whether or not a person is currently infected with a virus by identifying the presence of the virus's protein or glycoprotein.


Antibodies are proteins that have evolved to detect and react to harmful substances known as antigens. Antibody tests are useful, but they don't turn positive until around two weeks after symptoms have started. Antigen testing are a less expensive and quicker alternative to conventional diagnostic methods for infectious illness.