The detection of p24 antigen by ELISA is a simple cost-effective technique to demonstrate viral capsid (core) p24 protein in blood during acute infection due to the initial burst of virus replication after infection.
In order to maximize the detection of all infected individuals, including those
in early infection, antibody, antigen, and viral RNA tests should be used. However, viral RNA tests are expensive, time consuming, and unavailable in many laboratories.