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Source: http://www.yomiuri.co.jp/dy/national...25TDY02303.htm
30% of new-flu cases initially tested negative
The Yomiuri Shimbun
About 30 percent of people infected with the new strain of influenza initially tested negative in a commonly used screening procedure for the new flu, according to a survey by the National Institute of Infectious Diseases.
The error reportedly is due to variances in the amount of virus in a person's body after symptoms first appear.
The test almost always proved accurate when conducted the day after symptoms first appeared.
But in cases where the test was performed on the day symptoms first manifested, or two days later, about 40 percent of people infected with the virus were judged not to be infected.
The institute points out that negative test results do not necessarily mean a person is not infected with the new flu. The Health, Labor and Welfare Ministry has instructed medical institutions to use the test kit at appropriate times.
The testing kits, which are used at medical institutions and public health centers, includes cotton swabs used to obtain mucus from inside the nose and other places. Changes in the color of mucus-bearing test paper show about 10-15 minutes later whether infection exists and whether it is type A or type B virus.
Generally, gene tests or polymerase chain reaction (PCR) tests are carried out to confirm the virus only when the test kit proves positive for type A virus.
However, when a research team from the institute investigated 43 people who were confirmed as being infected with the new flu in Kobe, they found that 20 people, or 47 percent, had proved negative for type A virus in the initial test.
These same individuals were confirmed to be infected with the new flu through PCR testing.
In Osaka Prefecture, it was learned that seven out of 23 people, or 30 percent, confirmed to be infected with the new flu had initially tested negative when the test kit was used.
Only one person in eight in Osaka Prefecture tested negative when the test was performed the day following the initial appearance of symptoms. However, three people in seven, or 43 percent, tested negative when the test was conducted the same day or two days after symptoms first appeared.
(May. 25, 2009)
30% of new-flu cases initially tested negative
The Yomiuri Shimbun
About 30 percent of people infected with the new strain of influenza initially tested negative in a commonly used screening procedure for the new flu, according to a survey by the National Institute of Infectious Diseases.
The error reportedly is due to variances in the amount of virus in a person's body after symptoms first appear.
The test almost always proved accurate when conducted the day after symptoms first appeared.
But in cases where the test was performed on the day symptoms first manifested, or two days later, about 40 percent of people infected with the virus were judged not to be infected.
The institute points out that negative test results do not necessarily mean a person is not infected with the new flu. The Health, Labor and Welfare Ministry has instructed medical institutions to use the test kit at appropriate times.
The testing kits, which are used at medical institutions and public health centers, includes cotton swabs used to obtain mucus from inside the nose and other places. Changes in the color of mucus-bearing test paper show about 10-15 minutes later whether infection exists and whether it is type A or type B virus.
Generally, gene tests or polymerase chain reaction (PCR) tests are carried out to confirm the virus only when the test kit proves positive for type A virus.
However, when a research team from the institute investigated 43 people who were confirmed as being infected with the new flu in Kobe, they found that 20 people, or 47 percent, had proved negative for type A virus in the initial test.
These same individuals were confirmed to be infected with the new flu through PCR testing.
In Osaka Prefecture, it was learned that seven out of 23 people, or 30 percent, confirmed to be infected with the new flu had initially tested negative when the test kit was used.
Only one person in eight in Osaka Prefecture tested negative when the test was performed the day following the initial appearance of symptoms. However, three people in seven, or 43 percent, tested negative when the test was conducted the same day or two days after symptoms first appeared.
(May. 25, 2009)
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