infections
COVID 19
Diagnosis of COVID 19
Tests to identify the virus Doctors suspect COVID-19 in people who have symptoms of the infection. Recent close contact with someone who has COVID-19 increases the likelihood of infection. People who suspect they may have COVID-19 should call their doctor before being tested and before arriving at a clinic so appropriate precautions can be taken. The following people should be tested for COVID-19 (also seeCOVID-19 Testing): People with Symptoms — People who have been in close contact with a COVID-19–infected person but do not have symptoms—get tested at least 5 days after exposure; wearing a mask is recommended until negative test results are received People asked to test because of school, workplace, health care setting, or government requirements People who took part in activities that put them at higher risk for COVID-19, such as attending large social gatherings or being in crowded indoor settings without correct and consistent masking, may also want to be tested. There are two types of tests to diagnose COVID-19 infection: NAAT (nucleic acid amplification test) Antigen tests There are multiple types of NAATs. RT-PCR (real-time reverse transcriptase–polymerase chain reaction) tests, often simply called PCR tests, are the type of NAAT that have the highest sensitivity and specificity, meaning they are more accurate and thus the preferred initial test for COVID-19. RT-PCR tests can be done on upper and lower respiratory secretions (samples from nasal or oral swabs or saliva) to identify the virus. Antigen tests can be done at home or in a health care setting, but they are generally less accurate than NAATs, including RT-PCR tests. (See alsoFDA: At-Home COVID-19 Antigen Tests-Take Steps to Reduce Your Risk of False Negative Results.) Therefore, it may be necessary to confirm some antigen test results (for example, a negative test in a person with symptoms) with a RT-PCR or other NAAT. Many antigen test kits also recommend repeating the test over several days to increase the likelihood of detecting infection. Also, some tests may not detect the Omicron variant or other emerging variants (seeFDA: SARS-CoV-2 Viral Mutations: Impact on COVID-19 Tests). Another type of test is called an antibody test. Antibody tests (also called serologic tests) are not used for diagnosing current infections. Antibody tests help determine whether the person being tested was previously infected, which is important for tracking cases and studying the virus. 