The two red lines we commonly use are the antigen detection kits that are judged to be positive, antigen self test kit,which are based on the principle of double-antibody sandwich ELISA.
The sample was dropped on the sample pad, and then passed through the binding pad, detection line (T line) and quality control line (C line) on the reaction pad in sequence by liquid chromatography. The binding pad contains colloidal gold or latex spheres labeled with antibodies that move with the sample.
When the sample contains virus, the virus binds to the antibody on the surface of the chromogenic component on the binding pad, and the T line turns red. The excess chromogenic sphere will continue to move forward through the T line. When it reaches the quality control line (C line), it will bind to the coated antibody and fix the color component, so the C line will turn red.
However, if the sample does not contain virus, antigen-antibody specific binding does not occur as the sample passes through the binding pad until it reaches the C line and binds to the secondary antibody there, resulting in color development, which proves that the chromatography process is smooth. At this point only the C line turns red and is negative.
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