04-20-2020, 11:32 AM
(04-20-2020, 09:42 AM)michaelsean Wrote: I forgot to get back to this. They were tested for the flu ad it was negative. Now I imagine you can't test for "the flu", but you have to test for suspected strains. Would it be possible there was a flu virus they didn't know was here and didn't test for it?
The simple answer to your question is, yes. Although it would still most likely be strain A or B, a subtype could mutate making testing less accurate.
Most places have rapid antigen testing for the flu. Similar to your rapid strep screen. It is quicker, cheaper, and provides results faster. Plus you can perform more than one test at a time. But, the test we use has a false negative rate of 30-40% which means 3-4 patients out of every 10 has the flu despite the test telling you they don’t. A negative flu test doesn’t rule out the flu.
It is still recommended you treat the patient for the flu if they are high risk and the physical and history is consistent with the flu and it is flu season. Tamiflu is probably prescribed most often for the flu, but it’s efficacy is overblown by the manufacturer. The Cochrane Review is a well respected independent research watchdog for the medical community. They have determined most of the manufacturer’s claims aren’t supported by the data. For instance, the manufacturer claims Tamiflu can help you feel better 2-3 days faster. The Cochrane Review reports the research indicates it is actually less than 8 hours. Maybe. A prescription of Tamiflu use to cost about $200 without insurance. I wouldn’t pay $200 to maybe feel better in 8 hours. But, of course the manufacturer claims the Cochrane Review is wrong. But, try convincing a patient that after seeing a Tamiflu commercial on TV.
PCR testing is more accurate with a false negative rate of usually 10% or less, but it is more expensive, takes longer, and requires the purchase of a machine to run the test which can only process one swab at a time which takes about 15 minutes so you can only test 4 patients/hour.
A quick check of a lab reference lists false negative rate of 30-50% for rapid antigen flu testing and up to 33% for PCR flu testing.
Again, bottom line, a negative flu test doesn’t mean the patient doesn’t have the flu.
Many times I don’t even test for the flu if it won’t change the treatment plan. Meaning if they are high risk with flu symptoms during flu season I’m going to treat them for the flu (after ruling out other causes) and a negative flu test won’t change that so there is no point to performing a flu test, but it would increase the patient’s bill by about $90 dollars or more.