Testing for current infection
Viral tests, sometimes called diagnostic tests, can detect if you have SARS-CoV-2, the virus that causes COVID-19. There are two types of diagnostic tests: molecular and antigen.
A positive COVID-19 test (molecular or antigen test) means the person who took the test has COVID-19 and can spread it to others. If you get a positive test result, you should stay home and away from others. This advice does not change if you get a second test that is negative.
Your close contacts will also be asked to stay home and away from others (quarantine). This advice does not change if they get tested and the result is negative. learn more here.
It generally is not recommended that people get tested again after getting a positive result. However, those who work in health care and long-term care may need to retest to confirm a negative result.
PCR and other molecular amplification tests detect the virus’s genetic material.
- Most accurate tests for detecting the virus that causes COVID-19.
- Given with a nasal swab, oral (throat) swab, or by taking a saliva sample.
- Nasal swab: A nasal swabs looks like a long Q-tip. It is inserted about two inches into your nose and swirled around for a few seconds. The swab is then removed and sent to a lab for testing. You may experience a tickling sensation while the swab is in your nose, and after it is removed, you might sneeze or have runny eyes for a moment or two. Nasal swabs are fast and accurate, and they’re a good option for most people.
- Saliva test: Saliva tests are self-administered; this means that after you are shown how to perform the test, you’ll do it by yourself. You will spit several times into a funnel attached to a tube, and then screw on a cap to complete the test.
- If you are at a semi-permanent testing site, you will then hand your sample to a supervisor; if you are performing the test at home, you will put the sample into a prepaid UPS envelope and send it out. Most people need 10-12 minutes to make enough spit to fill the tube. Saliva tests are more comfortable than nasal swabs and just as accurate, but they may not be a good option for those with low saliva production, such as very young children or those who have suffered a stroke.
- Used whether or not you have symptoms.
- A positive PCR or other molecular amplification test result is considered a confirmed case of COVID-19, and public health workers will follow up with the person to give recommendations for how long to stay home.
Antigen tests, sometimes called rapid tests, look for specific proteins on the surface of the virus.
- Produce results more quickly than other tests.
- May not be as accurate, especially for people who do not have symptoms.
- Given with a nasal swab.
- A positive antigen test result is considered a probable case of COVID-19, but they are still considered cases and a public health worker will follow up with the person to give recommendations for how long to stay home.
Testing for past infection
Antibody tests, also called serology tests, tell if someone may have had SARS-CoV-2, the virus that causes COVID-19, in the past.
- Given by drawing blood via a finger stick.
- Cannot detect if you currently have COVID-19, only if you have had it in the past.
COVID-19 diagnostic testing is done to find out if you’re currently infected with SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19).
The U.S. Food and Drug Administration (FDA) approved these types of tests for diagnosing a COVID-19 infection:
- PCR test. Also called a molecular test, this COVID-19 test detects genetic material of the virus using a lab technique called polymerase chain reaction (PCR). A fluid sample is collected by inserting a long nasal swab (nasopharyngeal swab) into your nostril and taking fluid from the back of your nose or by using a shorter nasal swab (mid-turbinate swab) to get a sample.
- In some cases, a long swab is inserted into the back of your throat (oropharyngeal swab), or you may spit into a tube to produce a saliva sample. Results may be available in minutes if analyzed onsite or a few days — or longer in locations with test processing delays — if sent to an outside lab. PCR tests are very accurate when properly performed by a health care professional, but the rapid test can miss some cases.
- Antigen test. This COVID-19 test detects certain proteins in the virus. Using a long nasal swab to get a fluid sample, some antigen tests can produce results in minutes. Others may be sent to a lab for analysis.A positive antigen test result is considered accurate when instructions are carefully followed, but there’s an increased chance of false-negative results — meaning it’s possible to be infected with the virus but have a negative result. Depending on the situation, the doctor may recommend a PCR test to confirm a negative antigen test result.
A PCR test called the Flu SC2 Multiplex Assay can detect any of three viruses at the same time: the COVID-19 virus, influenza A and influenza B (flu). Only a single sample is needed to check for all three viruses, and this could be helpful during the flu season. But a negative result does not rule out the possibility of any of these infections. So the diagnostic process may include more steps, depending on symptoms, possible exposures and your doctor’s clinical judgment.
How you prepare
Whether or not you have symptoms, plan to wear a face mask to and from your doctor’s office or the testing center, and have anyone who comes with you wear one, too.
- If you think you may have COVID-19, call your doctor’s office or your local health department to review your symptoms and ask about testing before you go in, so staff can prepare for your visit, wearing personal protective equipment.
- If you have no symptoms but you’ve been in close contact with someone who has COVID-19, follow the testing advice of your doctor or public health department. Having a COVID-19 test 5 to 7 days after you were close to the person with COVID-19 is best. If you’re tested too soon, the test may not detect the virus.
If you think you may have COVID-19, call your doctor’s office to review your symptoms, if any, and ask about testing. Then your doctor and other staff can prepare for your visit, wear personal protective equipment, and give you instructions about where to go and how the test will be done. Plan to wear a face mask to and from the testing center, and have anyone who accompanies you wear one, too.
If you have no symptoms and have not knowingly been in contact with someone infected with the COVID-19 virus, but you want to get tested, ask your health care provider whether and where testing is available. Or you can call your state or local health department or visit their website for information on testing.