Indian-origin scientist develops TB test that reveals patients at risk

October 21st, 2008 - 2:35 pm ICT by ANI  

Washington, Oct 21 (ANI): A new blood test, developed by Professor Ajit Lalvani, a Wellcome Trust Senior Clinical Research Fellow at the Centre for Respiratory Infection at Imperial College London, can reveal which patients may develop active tuberculosis (TB) much more precisely than the 100-year old TB skin test.

Patients with active TB experience the symptoms of the disease, which include fever, persistent cough, and loss of appetite, whereas patients with the dormant, ”latent” form of TB do not. Treatment can prevent many patients with latent TB from progressing to active TB.

Unlike the blood test, the skin test commonly gives falsely positive results if a patient has previously been vaccinated against TB.

According to the researchers, the blood test will allow doctors to identify and treat those who need preventative treatment whilst reducing the numbers treated unnecessarily, thus avoiding the attendant risks of drug side-effects.

For the study, the researchers looked at 908 children in Istanbul, Turkey, who had recently been exposed to TB in their household. Of these, 594 tested positive for latent TB using the ELISpot blood test, the skin test, or both.

Of 550 children who tested positive for TB with the skin test, 12 went on to develop active TB. Fewer children tested positive for TB with the blood test (381), but the test still picked up 11 of the 12 children who went on to develop active TB.

Children with a positive ELISpot blood test result had approximately a four-fold higher risk of developing TB disease than children with a negative result.

A higher proportion of children with a positive ELISpot blood test result developed TB disease compared to children with a positive TB skin test.

As a precautionary measure, 76 percent of the children in the study had been given prophylactic treatment to prevent them from developing active TB.

This meant that the researchers could not determine the proportion of children who would have gone on to develop active disease had they remained untreated.

However, the researchers identified a significant risk for children with a positive ELISpot blood test result of developing active TB, despite the majority having received treatment, and this risk is therefore an underestimate of the risk in untreated children.

The ELISpot test works by detecting a protein signal, known as interferon-gamma, released by white blood cells of the immune system in response to TB infection.

The study is published today in the journal Annals of Internal Medicine. (ANI)

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