Answer
Authorized assays for viral testing include those that detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleic acid or antigen. Viral (nucleic acid or antigen) tests check samples from the respiratory system (such as nasal swabs) and identify if an infection with SARS-CoV-2 is present. Viral tests are recommended to diagnose acute infection. Some tests are point-of-care tests, meaning results may be available at the testing site in less than an hour. Other tests must be sent to a laboratory to analyze, a process that may take 1-2 days once received by the laboratory. Testing the same individual more than once in a 24-hour period is not recommended.
Diagnosis of coronavirus disease 2019 (COVID-19) requires detection of SARS-CoV-2 RNA by reverse transcription polymerase chain reaction (RT-PCR), which is better using nasopharynx samples compared to throat samples. [1] Lower respiratory samples may have better yield than upper respiratory samples.
SARS-CoV-2 RNA has also been detected in stool and blood. [1] The presence of SARS-CoV-2 RNA in blood may be a marker of severe illness. Older patients and those with severe illness requiring hospitalization may shed viral RNA over longer periods (median range of viral shedding among hospitalized patients: 12-20 days).
There have been reports of concurrent infection with SARS-CoV-2 and other respiratory viruses. [1] Detection of another respiratory pathogen does not rule out COVID-19.
