What Exactly Is an Antigen?
An antigen is any foreign or toxic substance recognized by your immune system as not belonging in your body. Antigens can be viruses, allergens, or even chemicals that cause the body to launch an immune response in order to combat illness or infection. Antigens are required to initiate the antibody production process.
What Exactly Is an Antibody?
An antibody is a protein produced by your immune system in response to the presence of a foreign substance in your body. When your immune system detects a virus, bacterium, allergen, or other substance, it produces proteins (antibodies) to neutralize similar substances in the future.
COVID-19 Antigen vs. Antibody Testing
In response to the COVID-19 pandemic, scientists developed antigen and antibody tests. Each test serves a specific purpose and is used in a variety of situations.
COVID-19 Antigen Tests: What Are They?
Antigen tests are widely used in the detection and diagnosis of respiratory infections such as influenza, respiratory syncytial virus (RSV), and SARS-CoV-2.
Because the presence of antigens is the first sign that a virus has entered your body, antigen testing aids in the detection of a current viral infection. Antigen tests are typically used as point-of-care diagnostics. In the case of COVID-19 testing, you could have it done in a lab, at your doctor's office, or even at home.
A swab is usually used to collect a fluid sample from your nose or throat for these tests. In the test kit, the sample is mixed with a chemical known as a reagent, and the results are ready in 15 to 30 minutes. 3
Antigen tests are typically not as sensitive as real-time reverse transcription polymerase chain reaction (RT-PCR) and other nucleic acid amplification tests (NAATs) that identify virus genetic fragments. Nonetheless, they contribute to the widespread availability of quick test results.
What Exactly Is Antibody Testing?
Antibody testing determines whether your body's immune system reacts to an antigen. In the case of COVID-19, antibody testing is available but not recommended for general public use.
Antibody testing should not be used to detect or diagnose a COVID-19 infection, whether current or active. These tests should also not be used to determine whether an unvaccinated person has been infected and requires immunization, or whether COVID-19 vaccination was effective.
Finally, antibody tests should not be used to justify exemptions from COVID-19 personal protective equipment (PPE), such as face masks.
Choosing the Best COVID-19 test kit
An antigen test is the best way to determine if you are currently infected with COVID-19. You can use a rapid antigen test at home or have the test done in a lab or by a healthcare provider. Your results will show that you are currently infected with the SARS-CoV-2 virus. 4
Although antibody tests for home use are available, they should not be used to detect an active infection. Even if you are attempting to test for a previous infection, the results of an antibody test may not be accurate until one to three weeks after you were infected.
Conclusion
Antigen tests are available in labs, clinics, healthcare provider offices, and as at-home tests to detect a current COVID-19 infection. Antibody tests will not detect an active infection, but they may indicate whether your body has produced antibodies against SARS-CoV-2 as a result of a previous infection or vaccination.
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