Quick flu tests, fail the test

Published

Specializes in Acute post op ortho.

thursday, aug. 6 (healthday news) -- doctors can't rely on rapid tests to diagnose the pandemic h1n1 swine flu, say u.s health officials who evaluated three kits and found that they miss many infections.

the tests do a better job detecting seasonal flu than h1n1 flu, the u.s. centers for disease control and prevention reported. sensitivity for the h1n1 swine flu was just 40 to 69 percent.

"these are rapid tests that the physician would do in the office while the patient is waiting," said michael shaw, associate director for laboratory science in cdc's influenza division and the report's co-author. "these tests can sometimes provide misleading results."

a quick flu test is just one diagnostic tool, shaw said. "you shouldn't rely on it alone," he said. "there is no substitute for the judgment of the clinician."

because people might test negative but actually have the flu, shaw said, "we want to emphasis that the clinician should also go by the patient's symptoms and what they know is circulating in the community."

positive test results are accurate, however. "but a positive result only tells you it's flu, not what kind," shaw said. "it could be seasonal, it could be the pandemic strain." in either case, he said, doctors could start antiviral treatment with a drug such as tamiflu.

for people at high risk for flu complications, doctors should start treatment with antiviral medication and also get a test to confirm the results, which can take 24 hours, shaw said.

for the report, which is published in the aug. 7 issue of the cdc's morbidity and mortality weekly report, cdc researchers tested three commercially available rapid influenza diagnostic tests that can identify influenza a or b antigens in about 15 minutes. respiratory samples were used from 65 people known to have swine flu or seasonal flu.

the tests were able to detect the h1n1 swine flu only when a high percentage of the virus was in the respiratory sample, which means that many infections would be missed, according to the cdc.

shaw said that people will shed the most virus shortly after symptoms start so, for the most accurate results, it's important to give the test early.

fast flu tests have been in use for a couple of decades. "it's not news that these tests are not as sensitive as we would like them to be," shaw said. the question for the cdc was whether they would work with the new pandemic strain, he said.

dr. marc siegel, an associate professor of medicine at new york university langone medical center in new york city, said that anyone currently suffering from the flu has h1n1 swine flu.

right now, the test is not clinically important, siegel said. "if you got flu now, this is what you got," he said.

siegel agrees with the cdc that a flu diagnosis is best made on the basis of a person's symptoms and the flu strains in circulation.

http://www.nlm.nih.gov/medlineplus/news/fullstory_87834.html

so, the test is innacurate, 40 to 69% of the time, but diagnosis is to be made on a "basis of symptoms & the strain:confused: in circulation?

um, if the test is inaccurate as much as 69% of the time, how are we supposed to know what's in circulation?

and the real time pcr is not any better. it was granted an emergency status authorization, but only until april of 2010.

http://www.fda.gov/medicaldevices/safety/emergencysituations/ucm180064.htm

so, how many people really have the swine flu?

nobody knows.

Up Vote Up Vote ×
Specializes in School Nursing.

What they told us was that in my area, 99% of the flu cases they were seeing were H1N1 so they eventually stopped wasting money testing. Personally, I am starting to think it really does not matter if someone has H1N1 or other strains. As a school nurse, I treat them the same and exclude based on the same criteria. The docs and NPs that work with my kids are treating the illness just like any flu: Tylenol, Motrin, fluids, watch for complications, etc.

I guess it would be nice to know what strain someone has if you are in a high risk group for H1N1 (pregnant, immunosuppressed, etc), but I would err on the side of caution and assume that it is H1N1.

Up Vote Up Vote ×
What they told us was that in my area, 99% of the flu cases they were seeing were H1N1 so they eventually stopped wasting money testing.

Too funny. This is the line being fed in multiple areas around the country. "It's all swine flu, 99% of it." I sure as hell am not buying it. Maybe just a way to jack up the numbers of swine flu victims? Naww.....They wouldn;t do that!:no::yeah:

In other words, we're not testing so...

Paranoid parents + kid with "symptoms" = swine flu.

Bring on mass hysteria.

Up Vote Up Vote ×
Specializes in Too many to list.

Most people infected with the flu will have a self limiting illness. The majority will never be tested. Of those that were tested in the state of Alabama, here is just one week's worth of confirmed positive influenza A cases, and not surprisingly, most were the novel H1N1.

http://www.wltz.com/news/local/62410072.html

Of 51 positive specimens tested by the Bureau of Clinical Laboratories last week, 50 were confirmed as 2009 H1N1 influenza.

Why? Simply because there is no immunity to this new virus yet. With increasing numbers of infected cases, the pandemic virus will begin to replace the previous influenza A seasonal strains. The swine H1N1 then becomes a seasonal flu.

This pandemic will continue until the novel virus runs out of susceptible hosts. Swine H1N1 will be with us until it is replaced by another strain.

The 1918 pandemic went on for something like 22 months.

Up Vote Up Vote ×
Specializes in Acute post op ortho.
What they told us was that in my area, 99% of the flu cases they were seeing were H1N1 so they eventually stopped wasting money testing. Personally, I am starting to think it really does not matter if someone has H1N1 or other strains. As a school nurse, I treat them the same and exclude based on the same criteria. The docs and NPs that work with my kids are treating the illness just like any flu: Tylenol, Motrin, fluids, watch for complications, etc.

I guess it would be nice to know what strain someone has if you are in a high risk group for H1N1 (pregnant, immunosuppressed, etc), but I would err on the side of caution and assume that it is H1N1.

"They said"????

They admit that the test is inaccurate 40-69% of the time, depending on the brand test used.

The real time PCR is so inaccurate the FDA would only grant an emergency license until April 2010.

Yea, and Hannah Poling only has "autism like symptoms"

Yea.....that's what "they said"

Up Vote Up Vote ×
+ Join the Discussion