False Negatives in Bird Flu Patients in Vietnam
Recombinomics Commentary
February 23, 2005
>> But for three cases the Pasteur researchers - with NIID researchers observing - reconfirmed their earlier negative diagnosis. This is worrying as it suggests that the Vietnamese test is not sensitive enough to detect all cases. Tu says that the institute now plans to switch to the more sensitive test used in Tokyo and will ensure better training for its technicians. <<
Retesting of negative cases in Vietnam are turning up positives, indicating the earlier tests were not sensitive enough to detect positives. The false negatives (as noted in the Nature News above) are not a surprise. In many of the case clusters, initial tests on patients were inconclusive or negative. However, these new cases indicate the number of positives is higher, and there may be more human-to-human transmission.
Although these cases were from Vietnam, it seems likely that there are false negatives in Thailand also. They have yet to report a positive case this season. In one instances a boy had touched a dead chicken in a province that had confirmed cases of bird flu. Within a few days he had a high fever, lung involvement, and tested positive for influenza A, yet was said to be negative for H5N1. The next week another boy from the same province also developed symptoms, but test results were never reported.
The true extent of human infections or human-to-human transmissions by H5N1 in southeast Asia remains to be determined.
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