The lateral flow test seems simple enough – if the result is positive, a line appears next to the letter ‘T’ on the device, as well at the letter ‘C’.
I know the T means test and the C means control because I worked for several months with the team designing the award winning training for community testing.
We need to know the test is working properly so there has to be a control, validation, confirmation, etc indicator to confirm that the test works. Similarly, it’s easier to identify a positive as a test result so allocating T for the test also seems appropriate. The devices are generic and industry standard for use as narcotic, alcohol, pregnancy, testing etc. The only real difference is the contents of the paper strip inside the device that is coated with the materials to indicate Covid positivity. To re-machine the devices would be costly in terms of time, slowing production, and would have the potential to confuse clinical personnel.
When you know that explanation it makes sense and had never assumed that people would read the C as Covid.
Take care that the simple assumptions you make in the language you’re using aren’t being misinterpreted by the people who are using the materials you design.