There are two main types of at-home COVID-19 tests: PCR and antigen. Depending on your health priorities, you may want to look for one over the other. “A PCR, or polymerase chain reaction, home test [obtains saliva or] a sample of cells from the nasal passages, which is mailed back to a lab to be tested for COVID-19 DNA,” explains Dr. Sanjeev Jain. “If COVID-19 DNA is detected within the sample, the test would be considered positive, and if no DNA is detected, it would be considered negative.” But because DNA testing needs to be done in a lab, the rapid antigen tests performed entirely at home use a different metric to determine the presence of the virus. “[Rapid tests] are different in that they check for antigens, which are a specific type of protein found on the COVID-19 virus,” says Dr. Jain. “The COVID-19 antigen tests are able to give almost immediate at-home results by telling you whether or not the proteins found on the COVID-19 virus are detected in the sample.”