As the highly contagious Omicron variant continues to spread, more and more people are thinking about getting tested for COVID-19. You may be feeling under the weather, or you may have recently spent time with someone who has COVID-19. You may want to get tested before seeing family or friends, or attending a large indoor gathering.

With a number of different tests available, many people have questions about which test to take, when to take it, and what their results may mean. In this Q&A, Aaron E. Glatt, MD, MACP, FIDSA, FSHEA, Chair of the Department of Medicine and Chief of Infectious Diseases at Mount Sinai South Nassau, explains how you can decide which test may meet your needs.

What types of tests are available? What are the differences between them?

There are a number of different ways that we can diagnose a COVID-19 infection. None of them are perfect, and each has their benefits and disadvantages. Let’s break it into two groups of testing: We have antigen tests, and we have PCR tests. Each of them has a role, and each of them has a slightly different situation where they may be preferable.

So we start off with the antigen test. This is what most people use at home. These are the tests you can buy at your local pharmacy. They are often referred to as “rapid tests.” If an at-home test is positive, and you are symptomatic, it’s highly likely that you have a COVID-19 infection. If you are taking this test because you’ve been exposed to somebody with COVID-19, it is also likely that a positive test is reliable. On the other hand, when these tests are negative, they’re just not good enough to necessarily rule out that a person does not in fact have COVID.

The other type of test is a PCR test. There are many different types of PCR tests. Most PCR tests will take 24 to 48 hours to return your results. PCR tests are somewhat more sensitive than rapid antigen tests.  If your PCR test result is positive, that will almost always represent a true positive, meaning it is accurate and you do have COVID-19 or that you had it in the recent past. The issue with these tests, however, is that they’re so specific. That means they can remain positive even when somebody is no longer contagious, and they no longer have COVID-19. But in general, the PCR tests are very good. They can tell you with a little bit more certainty that you did have an exposure to COVID-19.

How do I know which test I should take?

We usually recommend you talk to your health care provider if you’re concerned that you may have COVID-19. If you have symptoms or if you were exposed to COVID, then you may want to go get an at-home rapid test. If your rapid test is positive, you should talk to your doctor to decide what, if any, additional tests need to be done. If you have more serious symptoms, you should be evaluated by a doctor no matter what the antigen or PCR test shows.

When should I get tested?

If you have symptoms, you should get tested right away. If you’re being tested because of an exposure, we usually recommend waiting at least two days, or 48 hours, before testing. There are always exceptions to the rule. But that’s the general recommendation.

How reliable are at-home tests?

There are different at-home tests, and some of them are more reliable than others. If you have symptoms, or you think there’s a likelihood that you do in fact have COVID, then these tests can be very useful if they’re positive.

If my test result is positive, what should I do?

The first thing to do is contact your doctor. This could be a telehealth visit. We want you reaching out to your provider and getting expert medical advice from the person who knows you and your medical history. Not everyone has the same level of risk. It’s best to have a health care provider decide what evaluation needs to be done, and what potential treatments, additional testing, and ongoing monitoring you may need.

If my test result is positive, when should I retest?

There isn’t necessarily a reason to retest if you’re positive and your clinical care is being handled and you’re doing better. Typically, we wait a certain length of time to decide that a person is no longer contagious, and that they can stop isolating. That may be a five day period of time, assuming your symptoms are resolving and you have no fever. After that, we recommend that you be extremely careful in terms of distancing and wearing a mask whenever you’re going indoors among other people for at least an additional five days. For somebody who’s having a little bit more of a complicated clinical course—for example, they are having symptoms that aren’t resolving or they’re having persistent fevers—then you can’t assume that in five days, they’re no longer contagious. This should be something that your doctor helps you decide based upon your particular symptoms and medical history.

If my test result is negative, does that mean I’m good to go?

Anyone who has symptoms should not be going into public gatherings with other people. If they do have to go indoors, they should be wearing a mask and distancing as much as possible. A negative test doesn’t mean you don’t have COVID, and it doesn’t mean you can’t be contagious. Even if it’s not COVID, it might be the flu or some other virus that could be contagious to other people. As a result, you should really try and protect everybody from whatever illness you may have.

If I have symptoms, but my test was negative, what should I do?

In that situation, there are additional tests that you can take, such as testing for the flu or additional testing for COVID-19. You should talk to your doctor if you have ongoing symptoms and you have a negative COVID test. It can be a telehealth discussion. You should speak with your doctor, who knows you, and knows your background and your risk factors for serious illness.

Why are testing and vaccination still important?

It’s very important that patients realize that while the press reports that Omicron is a mild illness—you just get a little bit of flu-like symptoms, and you’re fine—that’s not really true for everybody. If you’re not vaccinated, Omicron can cause severe illness. Even in vaccinated people, if they’re not boosted, they are still more likely to get into trouble. So the best recommendation at this point is to get a booster dose of the vaccine if you’ve gotten vaccinated, and certainly, if you haven’t been vaccinated, this is still a great time to get vaccinated.

A misconception is that the vaccines don’t work because there are breakthrough infections. Nothing can be further from the truth. These vaccines are phenomenally successful in preventing death, in preventing serious illness, in preventing admissions to the hospital. Omicron, while “milder” than the Delta variant, can still cause all of these things for some people. It’s critically important for everyone to protect themselves, protect their loved ones, and protect their community by getting vaccinated.