A friend had the symptoms but only the third test showed positive. It can take a while for the disease to show in your snot.
Having done a couple home tests by different makers I can tell that it's not too tempting to dig deep and long enough with the stick. Also, the instructions can be quite hard to understand: On the last package of five it read that one should push a hole through the area marked with a circle. There was also a drawing of a brick of sorts, a flat 3D rectangle. It took me a while to figure out that they meant the box of five instead of the test block as the proportional dimensions of the drawing illustrated a single test carton instead of the family pack... The fever of 38.6 C/101.5 F may also have affected my logical thinking.
Anyhow, there's many ways a first timer or a sick person can fail in performing the test so a bigger pack is a valid option.
