Questions Over Accuracy of Swine Flu Tests, Vaccinations
Current swift flu tests might miss several cases of the new swine flu strain, researchers at the U.S. Centers for Disease Control and Prevention announced Thursday.
The correctness of the tests varied from 40% to 69% in finding the swine flu, the CDC team noted.
The findings verify the CDC’s worries that the quick tests given in the doctor’s offices are not completely trustworthy for detecting H1N1 infections.
Three of the most popular tests were good at finding seasonal flu strains, detecting 80% of H3N2 infections, the CDC noted. However, in general, the agency recommends treatment based on symptoms.
"The recent appearance and worldwide spread of novel influenza A (H1N1) virus has highlighted the need to evaluate commercially available, widely used, rapid influenza diagnostic tests," the researchers said in the CDC’s weekly report published over death and disease.
The research team at CDC’s influenza section reviewed three tests: BinaxNow, made by Inverness Medical Innovations, Becton Dickinson’s Directigen EZ Flu A+B test and Quidel’s QuickVue.
They collected and used 65 respiratory specimens gathered in April and May that had tested positive for swine flu and/or the seasonal flu.
All had been initially tested using a slow but very accurate test called real-time reverse transcription-polymerase chain reaction, or rRT-PCR.
"The results showed that, although the (rapid tests) were capable of detecting novel A (H1N1) virus from respiratory specimens containing high levels of virus, the overall sensitivity was low," the CDC team wrote.
The QuickVue test found 69% of the swine flu cases, the Directigen test detected 49% and BinaxNow found 40%.
The World Health Organization reported that there are 162,230 confirmed cases of the swine flu and 1,154 deaths, but the CDC insists that over a million people in the United States have the virus.
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The majority of public health officials have stopped trying to get gather counts of how many are sick.
The CDC’s study points out that even if patients visit the doctor and are tested, the instant tests are not completely reliable.
This year’s flu season will be incredibly different. Although a lot of people will only need one shot for the seasonal flu virus, two others will be needed to protect against the new swine flu.
"We’d like to get to Job 1 and get most of it done," said Dr. William Schaffner, a Vanderbilt University flu expert, referring to seasonal flu vaccinations. "Get it done before we start to tackle Job 2," the more complex task of swine flu vaccinations, he added.
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