Dear King of many hearts around this terrestrial ball, greetings to you. As the title reads
1.I would like to know as to why the 20 min mark for reading results
2. Why some people sero convert in two weeks and some longer from the time of initial infection.
Thanking you, your sincerely.. Zambian counseller.
Why shouldn't rapid tests be read beyond the recommended 20- 40 minute time limit? Well, the same reason you wouldn't bake a pie for an additional several hours after it was fully cooked. You'd burn the pie and ruin it to the point it would no longer be appetizing or even edible! The immune-chemical reaction used in rapid HIV tests is designed to be read at a certain point. Beyond that the reaction and chemicals can change, making interpretation more difficult to assess and less accurate.
This involves many factors, including viral factors (viral strain, viral load, etc.) and host factors (immune system integrity, concurrent illnesses, etc.).