If you’re wondering about the differences between all of the COVID-19 tests, you’re not alone.

As cases of the COVID-19 Omicron subvariant BA.5 continue to increase across the United States, many people who have either been exposed or have symptoms of the SARS-CoV-2 virus are taking tests to see whether they are positive.

Several testing options are available, including at-home rapid antigen tests, RT-PCRs, and antibody tests.

But knowing which COVID-19 test to take and when to take it can be confusing.

Below we answer some of the most frequently asked questions about COVID-19 testing.

There are three Food and Drug Administration (FDA) approved COVID-19 tests in the United States:

  • rapid antigen tests, such as at-home tests
  • molecular tests, such as polymerase chain reaction (PCR) tests
  • antibody or serology tests

Rapid antigen and molecular are diagnostic tests that indicate whether you have a SARS-CoV-2 infection. You can take these tests at home, in your doctor’s office, at a testing site, or laboratory using a nasal swab or saliva sample.

According to a May 2021 review, at least one-third of all COVID-19 cases are asymptomatic, with almost 75% of people with a positive PCR test remaining asymptomatic for the duration of the illness.

So, even if you’re not showing symptoms, diagnostic tests are recommended when you’ve been exposed to SARS-CoV-2, the virus that causes COVID-19. This is especially true for people who’ve come into close contact with a confirmed case.

An antibody or serology test is a blood test that checks whether you’ve been exposed to or have developed immunity to COVID-19. The Centers for Disease Control and Prevention (CDC) recommends serology tests approximately 1 to 3 weeks after a suspected SARS-CoV-2 infection.

Molecular and antigen tests are the main diagnostic tests that check for a SARS-CoV-2 infection. While both tests can detect active SARS-CoV-2 infections, they work differently.

Molecular tests such as PCR tests are often performed in a clinical or laboratory setting using nasal or throat swabs, or saliva samples. It generally takes about a day to get back the results of a PCR test.

PCR tests can be more accurate than antigen tests because they can detect much smaller amounts of COVID-19 genetic material in your sample. A positive test result indicates the presence of the virus.

Antigen or rapid tests work by detecting specific proteins on the surface of the COVID-19 virus.

While antigen tests are an option at most laboratories or community-based testing sites, they’re also available as at-home kits. These nasal swab kits can provide rapid results in about 15 to 30 minutes.

An antibody test checks for the presence of antibodies in your blood. Antibodies indicate an immune response to a SARS-CoV-2 infection. Antibody tests can’t detect active SARS-CoV-2 infections. But they’re helpful if you have:

  • been exposed to someone with COVID-19 in the past 14 days
  • had an asymptomatic SARS-CoV-2 infection
  • had COVID-19 symptoms but were unable to take a PCR test

They can also detect whether you’ve had a previous infection.

While at-home tests like the rapid antigen test are quick and convenient, they’re not always the most accurate.

When taking a rapid COVID-19 test, timing is important.

The CDC recommends testing when you experience COVID-19 symptoms or if you’re asymptomatic 5 days after exposure. The 5-day timing allows your body to develop a viral load that’s high enough to be detected by the rapid antigen tests.

In April, a study published in JAMA found that symptomatic individuals with an initial negative at-home test tested positive 1 to 2 days later when their viral load increased.

It’s important to note the high incidence of false-negative results with antigen tests. You can have an active SARS-CoV-2 infection but have a negative antigen test because your body has a low viral load.

This is why experts often recommend following up on any negative at-home tests with a PCR test.

A PCR test can be more accurate because it can detect the virus at much lower levels in your system than a rapid antigen COVID-19 test.

But you can receive a false negative test if you take a PCR test too early, like right after exposure. So, while you may have an active SARS-CoV-2 infection, there may not be enough viral genetic material in your sample for the PCR to detect.

Though PCR tests are suitable for detecting active SARS-CoV-2 infections, you should not use them to determine the end of your quarantine period.

Most people are no longer contagious 10 days after the onset of symptoms or a positive test. But because the tests can pick up tiny fragments of the virus, some people may be positive for weeks or more after they’ve recovered and are no longer contagious.

An antibody test can help determine whether you’ve had COVID-19 by measuring IgM, IgG, and IgA blood levels. The presence of these antibodies indicates that you’ve:

  • been exposed to a SARS-CoV-2 infection
  • built up immunity against the COVID-19 virus

While antibody tests can determine whether you’ve had past exposure to the virus, they can’t detect active SARS-CoV-2 infections.

If you’ve completed the CDC’s recommended guidelines for quarantine, an antigen test is more accurate in helping you determine whether to end or continue your isolation.

Also, newer testing methods are emerging, making it possible to get PCR-quality test results at home.

If you suspect you’ve been exposed to COVID-19 or are experiencing symptoms of illness, talk with a doctor right away.

In addition to providing advice on monitoring and evaluating your symptoms, a doctor can help determine which COVID-19 test is right for you.

While no testing method is entirely accurate, knowing the differences between the types of COVID-19 tests can help you choose the best for your situation.

Antigen tests like the rapid at-home tests are convenient, affordable options for at-home testing.

Though molecular or PCR tests take time to process, they’re highly sensitive and are more accurate at detecting an active SARS-CoV-2 infection.

If you suspect you’ve been exposed to COVID-19 and can’t take an antigen or PCR test, an antibody test can help determine whether you’ve had a past infection.

Regular testing is one of the key ways to stop the spread of COVID-19. To find COVID-19 testing near you, visit your state’s health department website or the Department of Health and Human Services to find a comprehensive list of community-based testing sites.