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A new way of diagnosing tuberculosis could lead to a faster and more accurate test for the disease, say scientists.

The research leader says that given adequate funding such a test could be available within a few years.

The method uses the relative proportions of key proteins in a patient's blood to determine if they have the disease.

One in three people are infected with the Mycobacterium tuberculosis bacterium, though only one in ten of those who carry the bacteria develop the disease. Tuberculosis (TB) kills roughly two million each year, mostly in developing countries.

Most deaths are preventable with early diagnosis and treatment. But often the best test available in developing countries is to search a mucous sample for TB bacteria. This method is only 50 to 70 per cent accurate and requires that three samples be taken on separate days.

The research published in The Lancet today (14 September) is based on the idea that different diseases cause distinctive changes in the types of proteins circulating in a patient's blood.

Each protein combination acts as a signature to indicate that the disease is present.

The team led by Sanjeev Krishna of St George's Hospital Medical School in the United Kingdom used 350 blood samples from patients in Angola, The Gambia, Uganda and the United Kingdom, roughly half of whom had the active form of the disease.

After determining the protein signatures of active TB, the researchers worked out how four proteins varied according to whether a person was infected or not. This allowed them to diagnose the disease with 78 per cent accuracy.

"We wanted to show that the concept works for diagnosing TB, so that in the end a much simpler test can be developed — perhaps something like a dipstick," says Krishna.

He told SciDev.Net that given the right funding, a simple, cheap and quick test that does not require electricity or any sophisticated machinery could be available in a few years' time.

Paul Van Helden, director of Stellenbosch University's Centre for Molecular and Cellular Biology in South Africa agrees that the research could lead to a more accurate diagnostic test.

He says that failed diagnosis, which can lead to a patient's death or chronic illness and to others becoming infected by the patient, "comes at great cost and in all likelihood a far higher cost than a more expensive diagnostic [tool]".

Earlier this month, the World Health Organization warned South Africa about its spread of 'extreme drug-resistant tuberculosis', which so far has infected about 160 people in the eastern province of KwaZulu-Natal.

The strain is not only resistant to first-line drugs, but also to three or more of the six classes of second-line drugs, and is caused by incorrect treatment strategies.

Link to full paper in The Lancet*
*Free registration is required to view this article.

Reference:
The Lancet doi 10.1016/S0140-6736(06)69342-2 (2006)

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