1. Viral testing

Viral (nucleic acid or antigen) tests check samples from the respiratory system (such as nasal or oral swabs or saliva) to determine whether an infection with SARS-CoV-2 is present.
Viral tests are recommended to diagnose acute infection of both symptomatic and asymptomatic individuals, to guide contact tracing, treatment options, and isolation requirements

2. Antibody testing

Antibody tests are not recommended to diagnose acute infection of SARS-COV-2
Serologic assays may be used to support clinical assessment of persons who present late in their illnesses when used in conjunction with viral detection tests.
In addition, if a person is suspected to have a post-infectious syndrome caused by SARS-CoV-2 infection (e.g., Multisystem Inflammatory Syndrome in Children; MIS-C), serologic assays may be used.
Serologic assays for SARS-CoV-2 infection are an important tool for surveillance and epidemiologic studies, such as understanding the transmission dynamic of the virus in the general population.
Unlike direct viral detection methods, such as nucleic acid amplification or antigen detection tests that can detect acutely infected persons, antibody tests help determine whether the individual being tested was previously infected—even if that person never showed symptoms.

Antigen tests are immunoassays that detect the presence of a specific viral antigen, which implies current viral infection.
Antigen tests are performed on nasopharyngeal or nasal swab specimens placed directly into the assay’s extraction buffer or reagent.
The tests are relatively inexpensive and can be used at the point-of-care
The currently authorized devices return results in approximately 15 minutes
Antigen tests for SARS-CoV-2 are generally less sensitive than viral tests that detect nucleic acid using reverse transcription polymerase chain reaction (RT-PCR).
Rapid antigen tests perform best when the person is tested in the early stages of infection with SARS-CoV-2 when viral load is generally highest
Rapid antigen tests can be used for screening testing in high-risk congregate settings to quickly identify persons with a SARS-CoV-2 infection to inform infection prevention and control measures, thus preventing transmission.