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Sars-scare firm stands by accuracy of tests

But the WHO calls for modified techniques to be assessed after wrong diagnosis

The private biotech firm that sparked a Sars scare when a test result wrongly indicated a woman had the disease this month has stood by the accuracy of its tests.

The firm said the woman had an infection that led to the positive result.

Albert Yu, founder and chairman of Hong Kong DNA Chips, insisted its positive finding must have been caused by contamination of the sample, which came from a 34-year-old patient of Tsuen Wan Adventist Hospital.

Dick Thompson, spokesman for the WHO's Sars centre in Geneva, said the DNA Chips' technique 'needs to be assessed'.

Under the WHO guidelines, all laboratories that showed a positive test result for the Sars virus are required to conduct the same test technique a second time.

Questions are being raised whether the modified diagnostic test developed by DNA Chips is too sensitive.

'The reason why we use a very sensitive technique is that we try to avoid any false negative,' Dr Yu said. He insisted that the positive test result was no aberration.

'Either this sample was contaminated with a very little amount of coronavirus or with something during the process.

'We have no way to find out until we have another sample.'

Dr Yu said his company subjected specimens from the patient to four different Polymerase chain reaction (PCR) tests - both conventional and real-time. His staff had developed enhanced real-time PCR, which is a modified version of the most sophisticated PCR method that has been used by hi-tech laboratories.

But Henry Niman, a US-based genetic sequencing expert, said HK DNA Chips would have to re-examine its tests because they were picking up a low level of coronavirus that all other tests were missing.

'Theoretically, the DNA Chips approach should work. It sounds like they had a false positive.'

The result prompted a health scare that led to the woman being transferred from the private Tsuen Wan Adventist Hospital to the public Princess Margaret Hospital on September 15.

A day later, the Department of Health said its tests and those that were carried out by Princess Margaret showed the woman did not have Sars. She was treated with antibiotics for pneumonia and discharged on September 22.

The incident prompted the Director of Health, Lam Ping-yan, to announce that the government will provide its Sars test kits free to all 12 private hospitals.

The WHO is holding a meeting on laboratory issues surrounding Sars next month in Geneva.

Asked if the world was prepared with adequate diagnostic tests for Sars II, Mr Thompson acknowledged inadequacies.

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