Another Bird Flu False Negative for Second Nurse in Thai Binh?
Recombinomics Commentary
March 17, 2005
>> Final testing of the National Institute for Hygiene and Epidemiology showed that specimens from a 46-year-old female nurse from Thai Binh, who was admitted to the Institute of Tropical Diseases on March 10 with bird flu symptoms, were tested negative to H5N1. <<
The above report of another false negative on the female nurse from Thai Binh suggests that the sensitivity of the PCR test in northern Vietnam is similar to the 20% sensitivity level in southern Vietnam. The nurse had clinical signs of avian influenza and exposures to H5N1 positive patient(s) and co-workers. Repeated negative PCR tests indicate that such tests should only be used for inclusion of patients. The repeated negative results on patients who clinically present as H5N1 positive should require outside testing by a lab with a more reliable test, such as the NIID lab in Tokyo.
In addition, antibody tests should be run on samples collected several weeks after the onset of symptoms. The antibody tests should be on serial samples to determine if the patient has a rising antibody titer to H5N1.
Until these more accurate tests are run, the patient should be assumed to be H5N1 positive. Limited testing using a test that has sensitivity of less than 90% should not be considered "final".
Moreover, the WHO should revise its case definition to reflect the fact that the PCR testing in Vietnam has a low sensitivity and should only be used to include patients. Negative results should require confirmation of multiple samples using a validated test with a markedly higher sensitivity level.
Continued reporting of false negative results and use of such data to exclude cases is scientifically flawed and counterproductive to controlling or understanding the spread of H5N1.
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