What does a rapid antigen test primarily detect in patients?

A rapid antigen test primarily detects the presence of viral proteins in a patient's sample, such as nasal swabs or throat swabs. These tests are designed to quickly identify specific proteins associated with certain pathogens, for instance, the SARS-CoV-2 virus responsible for COVID-19.

The detection of viral proteins is crucial because these antigens are produced by the virus during an active infection, allowing for a swift diagnosis. This method is particularly beneficial in clinical settings where time is essential for patient management and treatment decisions. Rapid antigen tests often provide results much faster than molecular tests, which look for genetic material from the virus.

In contrast, the other options relate to different testing methods. The presence of antibodies against viruses involves serological tests, which indicate past infections and not current active infections. The presence of viral genetic material refers to molecular tests, such as PCR (Polymerase Chain Reaction), which are sensitive but usually take longer to yield results. The presence of pathogens in blood typically pertains to blood cultures or similar assessments rather than antigen tests focused on specific viral proteins.