Rhiza Labs FluTracker Forum

Performance of Rapid Influenza Diagnostic Tests During Two School Outbreaks of 2009 Pandemic Influenza A (H1N1) Virus Infection --- Connecticut, 2009

http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5837a1.htm

"In this group of patients, although positive RIDT results performed well in predicting confirmed infection with pandemic H1N1 virus (positive predictive value: 92%), negative tests did not accurately predict the absence of infection (negative predictive value: 32%). These results affirm recent CDC recommendations against using negative RIDT results for management of patients with possible 2009 pandemic influenza A (H1N1) infection (2)."


HEY CDC, sounds like YOU ARE LISTENING.


Now lets hope the DOCTORS DO!

And in case you missed that
(negative predictive value: 32%)

That means that if you have three people with PH1N1
~ one of them will come back as a negative.

This test is NOT to be trusted for negatives. Now lets all pray the MD's all read the MMWR. I know the good ones do!

Actually, it's worse than that, Happy. Negative predictive value gives the percentage of patients with negative test results who are correctly diagnosed by the test. The probability of no disease being present if the test result is negative is only 32%, or stated another way, the percentage of people with negative tests results who actually DO NOT have flu is only 32%. Worse yet, as the prevalence of the disease you're testing for in the community goes UP, the negative predictive value of your test goes DOWN.

HOLY COW your right

I just had a friend (Phd) from Tennessee write me, she went to Oxford for a few weeks and just came back on the plane, she became very ill getting off the plane.
They tested her today with the Quidel kit and it was negative so they sent her home so she was asking me about this.
I sent the CDC's post to her for her to print up and give to her MD.
I think we should all hang onto a copy of that just in case.

It appears to be a slight adjustment for Quidel kit to work better, they are only a few bases off. I am not sure why they are still having this issue.