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Think you were exposed to COVID-19? Here’s what test you should take. | Opinion

Last Updated: 09/30/2020

Edward Lifshitz, Medical Director of the Communicable Disease Service of the New Jersey Department of Health

If you recently attended a wedding, a sporting event, or any other event where you think you could have been exposed to someone with COVID-19, you should consider getting tested. This is particularly important if you, or someone around you, is elderly or has a chronic health condition.

When it comes to which test to get, there is often confusion. Everyone wants to know their test result as soon as possible, but they also want to make sure that the test is accurate. Some tests are more likely to return a false negative result that can provide a false sense of security that could potentially —and unknowingly — lead to the spread of the virus to others.

It is always best to talk with your health care provider about which test is best for you. There are three different types of available coronavirus tests, and there are important differences between them.

An antibody test looks for the body's response to SARS-CoV-2, the virus that causes COVID-19. It is a blood test that is good at determining if you had the disease, but not good for determining if you have the disease. As such, antibody tests should not ordinarily be used to diagnose the virus. While there is evidence that antibodies may provide protection from infection, that has not yet been proven and therefore results of an antibody test should not be used to determine immunity.

On the other hand, viral tests, which look for parts of the virus itself, are "diagnostic" – finding SARS-CoV-2 means that the person has COVID-19. There are two very different ways in which this is done.

A molecular test is usually performed using a technique known as Polymerase Chain Reaction (PCR), which works by rapidly making millions to billions of copies of viral-related DNA. If there are even small amounts of this genetic material in the sample, it will be detected. Thus, PCR tests are very sensitive and they are also very specific. People who are undergoing surgical procedures may be asked to get a PCR test prior to surgery. A positive test is almost never wrong in determining that SARS-CoV-2 is present. Tests can be done on samples taken by nasal or throat swabs, and even by saliva.

However, since molecular tests are almost always performed in specialized labs, it is a relatively slow process. Results on tests done as an outpatient are rarely ready in less than a day and may take much longer. Since these tests require specialized equipment, supplies and trained personnel, they are also expensive. While most people will not have to pay the price, the typical cost is about $100-$200 per test.

The other viral test is an antigen test, which is much simpler and can be done in many doctor's offices using a nasal or throat swab. In the future, it might even be able to be done at home or in other non-medical settings.

An antigen test is fast – providing results in minutes – and costs much less than a molecular test. But there is a catch: It is much less sensitive than the molecular test. There needs to be more virus present before the test will turn positive. This means that an antigen test may sometimes be falsely negative, meaning a negative result cannot always be trusted. A positive test, suggesting that the virus is present, is usually reliable, although even here false positives are more likely than with a molecular test.

Which test should you get? Well – it depends. For people with symptoms, the most important thing to do is to get one of the two viral tests. If you have symptoms, get the quick antigen test if it is available. If it is positive, you can start isolating to protect those around you from the spread of the virus.

But if the antigen test is negative, you should get retested using a molecular test and be sure to isolate yourself until you receive the result.

For most people who do not have symptoms but want to be tested because they may have been exposed, the molecular test is the better choice. It can find small amounts of the virus that might be seen before symptoms start.

More information about the 300 testing sites available throughout the state can be found on the state's COVID-19 information hub.

And remember: Keep social distancing. Keep masking up. Keep washing your hands. If you have any doubts – get tested. If you do test positive, contact tracing is vital to stopping the spread of the virus so please take the call.