An antibody test is used to test for the presence of specific antibodies in the bloodstream. A swab test is a way of taking a sample for later testing by nucleic acid or antibody tests.

What is Antibody test?

Definition:

An antibody test is a way to determine if your body contains antibodies to a particular disease. It indicates if you have been exposed to a certain pathogen that causes illness.

How the test is performed:

In the case of COVID-19, the antibody test works as follows: the technician takes a small sample of blood by pricking your finger. The blood sample is then used in a test looks for two types of antibodies, IgG and IgM. While IgM happens soon when you are infected with COVID-19, it takes time for the IgG to be formed. It is important to understand that the presence of antibodies just means a person has been infected at some stage. The person may not be showing symptoms and may already have recovered.

Type of pathogens it is used for:

Antibody tests can be used to test for illnesses caused by viruses, for instance, COVID-19 and HIV. There are also antibody tests used for diagnosing bacterial infections such as tuberculosis.

Advantages:

It gives researchers a better idea of how many people have been infected with a particular pathogen; for example, it gives insight into the numbers infected with COVID-19, and also helps to determine if plasma donations are helpful in treating COVID-19.

Disadvantages:

Sensitivity can vary a great deal, for example with TB it can be accurate at anywhere from 63% to 85%. The COVID-19 antibody tests also are not 100% accurate.

What is Swab test?

Definition:

A swab test is when a sample is taken out of the back of the nose or throat for later testing to see if a particular pathogen is present. 

How the test is performed:

The technician uses a sterile swab which is usually about 6 inches in length. This swab is placed into the back of the nose or the mouth where it is turned a few times to collect a sample. The swab is then removed and the sample tested in some way. In the case of COVID-19, swab tests are usually later tested by RT-PCR methods. When testing for strep throat, an antigen test is performed on the throat swab.

Type of pathogens it is used for:

Swab tests are routinely done to test for the presence of Streptococcus, which causes strep throat. It is also used to obtain a sample for coronavirus testing. The sample is then tested by either an antibody or nucleic acid test, in the case of COVID-19.

Advantages:

A person can get a swab test done while sitting in their car since it is easy, quick and does not require special equipment. As a result many COVID-19 drive-up stations are set up in some countries.

Disadvantages:

The test can make a person feel uncomfortable and cause gagging because swabs are taken from the back of the throat and nose.

Difference between Antibody test and Swab test?

Definition

An antibody test is one where the aim is to detect the presence of a particular antibody. A swab test is a test in which a swab is used to collect a sample from the mouth or nose for later testing for the presence of a virus or bacterium.

Pathogens tested for

In the case of an antibody test, pathogens such as the particular viruses that cause COVID-19 or HIV are tested for. In the case of a swab test, samples are collected and tested for the presence of the COVID-19 virus or Streptococcus bacterium. 

Direct diagnosis of an illness

An antibody test is a direct way to find and diagnose the presence of a pathogenic organism. With a swab test, additional tests are needed because it is not a direct method for detecting pathogens.

Benefits

Since an antibody test is not based on nucleic acid, there is no need to go through a nucleic acid amplification step. A benefit of a swab test is that it easy and quick to do compared with taking a blood sample in a health center.

Drawbacks

A disadvantage of an antibody test is that it is generally not as sensitive or as accurate in the diagnosis of an illness as are other tests such as RT-PCR. A disadvantage of a swab test is that is uncomfortable for the patient and often causes gagging; it also means more testing is needed to look for the pathogen.

Table comparing Antibody test and Swab test

Summary of Antibody test and Swab test

• Both antibody and swab tests are used in the process of testing for particular illnesses.
• An antibody test is easy to do, but not as sensitive as nucleic acid tests. 
• A swab test is the collection of a sample to use for further testing for a pathogenic organism.
• Both swab tests and antibody tests are used when testing for the presence of COVID-19 virus.

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