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The BBC's Chris Hogg
"It will be two to three years before this test is widely available"
 real 56k

Friday, 22 June, 2001, 00:53 GMT 01:53 UK
More accurate TB test unveiled
TB test
Existing tests are not always accurate
Scientists have developed a blood test to identify tuberculosis in its earliest stages before any of the symptoms of the disease become apparent.

Its use may help doctors to screen people who have been in contact with a TB sufferer and reliably identify those who are infected long before they have actually developed the disease.


Appropriate application of this assay might significantly contribute to tuberculosis control

Dr Ajit Lalvani
The respiratory disease is a major cause of death worldwide, and several high profile outbreaks in recent months have highlighted the fact that it is once again becoming more common in the UK.

It is important people who have the disease are identified at the earliest possible stage, both so they can receive treatment, and measures can be taken to minimise the risk to others.

People with active TB of the lung are infectious to others and can infect, on average, 10 to 15 other people each year just by coughing, sneezing or talking.

More than 60 people linked to a Leicester school were found to be infected with TB after an outbreak earlier this year.

Public health officials admitted that if the original carrier had been diagnosed earlier, fewer children would have been infected.

The current test in use is the century-old tuberculin skin test (TST), also known as the Heaf test.

But it is not reliable because it can give false-positive results in people who have been given the anti-TB BCG vaccine, or exposed to other similar types of bacteria.

The new test has been developed by a team from Oxford University.

It is based on analysing blood samples for the presence of immune system cells that are activated by a protein produced by the TB bacterium, but not by any strains of the BCG vaccine.

Trials

Dr John Moore-Gillan
Dr John Moore-Gillan says TB is a major problem
The new test was trialled on 50 healthy volunteers who attended a contact-tracing clinic in London after having been exposed to TB in varying degrees.

It produced much more accurate results than the old TST test.

Lead researcher Dr Ajit Lalvani said: "Our assay (test) has the potential to be used to identify recently infected contacts and other individuals at high risk of tuberculosis infection in low prevalence countries.

"This assay could enhance containment of tuberculosis outbreaks and improve targeting of preventative therapy to people with latent tuberculosis infection.

"Appropriate application of this assay might significantly contribute to tuberculosis control, but only after larger studies with a longer follow-up have confirmed our promising results."

Dr John Moore-Gillan, of the British Thoracic Society, told BBC News Online the new test was a potential step forward.

He said: "The method we are using at present has not really changed for decades.

"TB research has been an incredibly neglected filed. This study shows what can be done when resources are diverted into research into TB.

Approximately a third of the total population of the world has been infected with the TB bacterium. But only a small percentage go on to become ill.

At present, approximately eight million people develop symptoms each year, and two million die.

The reasons why TB has become more common in recent years are not fully understood. However, an increase in travel is partly to blame.

The research is published in The Lancet medical journal.

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See also:

06 Apr 01 | Health
'I lost a lung to TB'
23 Oct 00 | Health
Sharp increase in tuberculosis
17 Aug 00 | Health
TB 'toughness gene' uncovered
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