An RSV test is a diagnostic test that checks for the presence of respiratory syncytial virus (RSV) in a fluid sample from the nose or throat. RSV is a highly contagious infection that affects the respiratory tract, including the lungs, nose, and throat. There are two types of tests commonly used to diagnose RSV infections:

• Rapid RSV antigen tests: These tests check a fluid sample from the nose for certain proteins from the RSV virus called antigens. They can provide results in an hour or less and are the most common test for RSV.

• Molecular tests called RT-PCR (polymerase chain reaction) tests: These tests look for genetic material from the RSV virus in the sample. They can find smaller amounts of the virus than antigen tests and are used for older children and adults who tend to have less of the virus in their noses than infants and younger children. Samples are usually sent to a lab for testing.

Other tests that may be done in conjunction with RSV testing include:

• Respiratory pathogens panel: A molecular test that checks for multiple respiratory viruses, including RSV.

• RSV antibody test: A blood test that measures the levels of antibodies the body makes after an infection with RSV. This test is mostly used to collect data for research purposes.

• Viral culture: A nasal fluid sample is taken to a laboratory, where it’s placed in a dish and observed to monitor the growth of the RSV virus. This test is not as sensitive as RT-PCR and antigen tests.

RSV testing is usually done during the "RSV season," the time of year when RSV outbreaks are more common. In the United States, RSV season usually starts in mid-fall and ends in early spring, but the season may vary in different parts of the country. RSV testing is primarily ordered for infants between the ages of 6 months and 2 years, the elderly, and those with weakened immune systems, such as those who have pre-existing lung disease or who have had an organ transplant.