# Case study 1

There is a patient who was suspected to be infected by Influenza virus.
The test which conducted yesterday showed negative result but the same test which done today shows positive result.
There are few reasons for this situation. The following are just some of the examples.

1. Laboratory -- The operator who conduct the test might have miss out some procedure during the first test.
2. Nurse -- The sample obtained is too little.
3. Manufacturer -- (Rare) The provided product is not functioning well.