Figure 3.

Mechanism of action of antigen tests. Point-of-care antigen tests typically are lateral flow assays and come with a test strip or cassette composed of multiple overlapping pads. The clinical sample needs to be placed in a tube containing the extraction reagent after collection, which disrupts the viral particle and exposes the viral proteins. Next, the sample is added to the sample pad, where it starts to travel via capillary action through the conjugate pad and conjugates with the fluorescence-labeled severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) detection antibody or the detector-antibody gold conjugate. Next, it flows through an analytical membrane striped with a capture antibody specified as the test line. Most tests include a control line after the test line to validate proper fluid flow and the activity of assay reagents. The final outcome might be read via an instrument or displayed as colored lines for naked-eye reading.