The 1. kit has expired and may deteriorate. At this time, if it is tested again, the background color of antigen detection may change color.
2. Failure to strictly follow the instructions, mistakes or mistakes in operation steps may also lead to discoloration of the background color of antigen detection.
3. If the antigen kit is left for too long, some related reactions may occur when exposed to air, and the background color of antigen detection may also change color.