What testing modality is most sensitive for detecting acute SARS-CoV-2 infection?

• A. NAAT/PCR
• B. Antigen testing
• C. Serology
• D. Chest radiograph

Answer: (A)

For acute SARS-CoV-2 infection, detecting the virus itself with a nucleic acid amplification test is the most sensitive approach. RT-PCR and other NAATs amplify viral RNA, so they can detect tiny amounts of virus even when the load is low, which is common early in infection or in mild cases. This high analytical sensitivity makes PCR the best option for confirming active infection.

Antigen tests, while fast and convenient, require higher viral loads to yield a positive result and are less reliable in the early or late stages when the amount of virus is low. Serology looks for antibodies, which usually develop several days after infection and reflect past exposure or immune response rather than an active infection. Chest radiographs are imaging tools that can show pneumonia but are not sensitive or specific for detecting acute viral infection themselves.