Antigen vs. Antibody: What is the difference?

As the headlines about the vaccine and testing mandates continue, many employers are looking to evaluate testing choices to understand what the different testing options mean for workplace COVID monitoring. One of the biggest questions at the heart of this discussion is the difference between antigen tests and antibody tests- including how the tests work, the purpose of the tests, how they are helpful, and more. 

Antigen versus Antibody: The Basics

An antigen test is typically administered by collecting a sample from your nose or throat using a long swab. A positive antigen test can be used to detect an active COVID-19 infection, while a negative antigen test means that no SARS-CoV-2 viral proteins were detected. However, it is essential to remember that a negative test does not entirely rule out a COVID-19 infection. If there are still concerns over a possible active infection, COVID-19 would need to be completely ruled out by a molecular test. 

An antibody test is typically administered by drawing blood from your arm or a finger stick. The blood is then analyzed to determine the level of antibodies in the blood. A positive result on an antibody test shows that there are antibodies in your system. However, these antibodies could be from either a previous infection or a vaccine. 

Meanwhile, a negative antibody test means there has not been a COVID-19 infection (or vaccine) previously. An antibody test does not confirm where or not a person is experiencing an active infection when the test is given. Lastly, depending on what antibodies are being measured, an antibody test may or may not be able to tell whether your body has begun to fight a COVID-19 infection or if you have been infected for several days. 

When they are helpful 

An antigen test is a great way to determine if someone has an active infection quickly. Additionally, this will also help testers know if someone is contagious to others. Lastly, it is traditionally less expensive than a molecular test. 

An antibody test will identify people who have been infected in the past – even if they were asymptomatic. An antibody test will also help to confirm if someone is vaccinated. Additionally, it can help determine if someone qualifies to donate convalescent plasma. In some instances, it can help determine when the COVID-19 illness occurred- based on the presence (or lack of) IgM and IgG. 

The testing process

As mentioned previously, an antigen test is administered with a swabbed sample from the nose or the back of the throat, and the antibody test requires a blood sample from the arm or a finger prick. Once a sample is retrieved, each test has a different process, and you can read about the rapid antigen and rapid antibody test procedures on the Medek website. At Medek, we understand that time is valuable, and that is why either Medek test can be administered and provide results within ten minutes for maximum convenience. 

One-stop testing shop 

Ultimately, your testing goals will determine what test or tests you may choose to administer in your workplace. If you are looking to ensure your staff is vaccinated, the antibody test will provide insight as to whether their status is as they claim. Suppose the goal is to test unvaccinated staff and visitors to ensure they are not bringing an active infection into your facility. In that case, you will want to test regularly with antigen tests. Still not quite sure? Don’t decide alone! Working with a testing partner will ensure you have the correct tests needed to keep your worksite safe and OSHA compliant. It’s not too late to partner with us and successfully implement your testing policy. Message us today!