How accurate are nasal swab flu tests? my sister had one yesterday @ our dr 's ofc, but it was neg for flu. she has fever, chills, is very achy, etc.

Accurate if positive: If a nasal swab flu test is positive, it is a very reliable result. The swab is nasopharyngeal, meaning the swab goes to the back of the nose to get a mucus sample. If it is negative, it is only somewhat reliable, which means a person with a negative result may still have influenza. A rough estimate is that 1 out of 4 people with cold or flu symptoms, who test negative, actually do have influenza.