Types of COVID-19 tests

COVID-19 testing is critical to slowing the spread of the pandemic, because you can be infected with the coronavirus and spread it to others even if you don’t have symptoms.

Knowing which test to get can be confusing. What kinds of COVID-19 tests are available? What is the difference between a PCR test and an antigen test? Antigen vs. antibody? What is the most accurate COVID-19 test? This chart can help you understand and choose.

ASU’s COVID-19 PCR test is free to anyone who wants one.

TestPCR (RT-PCR, qPCR or molecular) testAntigen (rapid) testLAMP (rapid home) testAntibody (serology) test
SummaryThe most accurate diagnostic test. It can tell you if you are infected with the coronavirus. ASU’s saliva tests are PCR tests. The fastest diagnostic test, but not highly accurate. Most useful for screening groups of people in settings where rapid or repeated testing is needed. This rapid at-home diagnostic test is similar to PCR but may be less accurate.Tells you if you had COVID-19 in the past. Not a diagnostic test. Do not use it to detect a current infection.
What is it?A PCR test detects genetic material from the coronavirus using a nasal swab, nasopharyngeal swab or saliva sample.An antigen test detects proteins from the coronavirus (called antigens) using a nasal or throat swab. The loop mediated amplification reaction (LAMP) test detects genetic material from the coronavirus using a nasal swab. Patients can run the test from start to finish at home.This blood test detects antibodies to the coronavirus. Antibodies are proteins your body produces to help fight off future infections. 
What does it tell you?positive result means you are infected with the coronavirus. A negative result means the virus was not detected.*positive result means you are infected with the coronavirus. A negative result means the virus was not detected.*positive result means you are infected with the coronavirus. A negative result means the virus was not detected.*positive result means you had the coronavirus in the past. Your body takes about 1-3 weeks after infection to develop antibodies.  A negative result means no antibodies were detected.A positive antibody test does not guarantee that you are immune to the virus. We do not know how much protection antibodies provide or how long they remain in the body.
How long does it take to get results?ASU typically delivers results on its saliva-based PCR tests within 48 hours. Other labs may take longer.Instrument run time is 15 minutes.  However, only a few samples can be run at a time and with sample collection this can take an hour or more.About 30 minutes to run the sample, but this is only available by prescription at home.Usually 1-3 days.
How accurate is it?This is the most reliable test available for COVID-19. However, it takes several days to build up enough virus in the body be measured. People who are tested early (up to 5 days after exposure) may test negative even if they are infected — a false negative. This is due to the incubation time of the virus, which takes a while to appear in body fluids. If you do not have symptoms, you should wait 5 days after you were potentially exposed to the virus before getting tested. PCR tests are not likely to produce false positives. If you get a positive test result, you can be confident that you are infected.This test is not as accurate as a PCR test. It is more likely to produce false negatives, especially after the first week of infection. This means you could be infected with the coronavirus even if you receive a negative test result. Also, like with PCR tests, people who are tested within 5 days after exposure may not have enough virus in their bodies to detect.Recent studies suggest that this test is only useful for individuals with symptoms. It does not detect the virus in asymptomatic or pre-symptomatic patients. If you have COVID-19 symptoms, you should follow self-isolation recommendations even if you get a negative antigen test result.This test is not as accurate as a PCR test. The false-positive rate appears to be higher, so you could get a positive result without having the virus. Also, like with PCR tests, people who are tested within 5 days after exposure may not have enough virus in their bodies to detect. In addition, the LAMP test is more subject to user error because it is self-administered. Results from home tests are not automatically submitted to the state for public health reporting or contact tracing efforts. This could hurt our efforts to understand and slow the spread of COVID-19.Antibody tests may produce false negatives if they are taken too soon after an infection, before antibodies appear. Also, we don’t know how long COVID-19 antibodies last, so they might eventually go away.  Some antibody tests may cross-react with other coronaviruses that are not SARS-CoV-2 (the virus that causes COVID-19). This could produce a false positive result.

*Remember: A COVID-19 test result only applies to the moment you were tested. If you are exposed to someone with the virus after taking a test, you could still become infected. For example, if you get a negative test before taking a trip, you could still catch the virus on the plane and spread it to others at your destination. Always take precautions to prevent the spread of COVID-19.

A dose of facts

Get answers to your COVID-19 questions and see our vaccine infographic.