New TB test means quicker and easier diagnosis fo...( A new blood test could enable doctor...),Health

A new blood test could enable doctors to rule out tuberculosis (TB) infection within days rather than weeks, according to a new study published this week in the journal Annals of Internal Medicine.

The study, by researchers from Imperial College London and the University of Oxford, shows that doctors can determine that a patient does not have tuberculosis with 99% accuracy when using the new blood test, ELISpot-Plus, in conjunction with a skin test known as tuberculin skin testing, already in use.

TB is difficult to diagnose because many of its symptoms, such as fever, fatigue, and loss of appetite, are also commonly found in many other conditions. The combination of ELISpot-Plus and tuberculin skin testing is able to rule out TB within 48 hours, providing a much quicker result than existing testing methods, for which results take up to several weeks.

The new test combination could prevent patients who do not have TB from being subjected to further lengthy TB tests, and allow doctors to begin investigating other explanations for such patients' symptoms.

The new study showed that ELISpot-Plus alone was accurately able to determine TB infection in 89% of cases and tuberculin skin testing alone was able to determine TB infection in 79% of cases. However, using both tests together was able to rule out TB infection with an accuracy of 99%.

The ELISpot-Plus test works by detecting signs of a particular response that occurs when the immune system encounters TB infection. The test looks for a type of protein known as interferon-Y. This is secreted by T cells in the immune system when they encounter antigens found in the bacterium mycobacterium tuberculosis, which causes most cases of TB.

The tuberculin skin test commonly gives falsely positive results if a patient has previously been vaccinated against TB, because vaccination causes a reaction in the immune system which looks very similar to its reaction against
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