Faster TB test results on the way

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A blood test which enables doctors to rule out tuberculosis (TB) infection in days rather than weeks has been developed by UK researchers.

It could prevent patients having to undergo lengthy investigations and allow them to begin treatment more quickly, they said.

TB is hard to diagnose because its symptoms, such as fever and fatigue, are associated with other conditions.

The research is published in the Annals of Internal Medicine.

Britain is the only country in Western Europe where TB is on the rise and London, which carries almost half the national burden, is Europe's TB capital.

At the moment, it can take quite a long time to figure out whether or not a patient has the disease, because it can mimic many different conditions and present in many different ways Professor Ajit Lalvani, study leader The blood test, developed by a team at Imperial College London, can determine that a patient does not have tuberculosis with 99% accuracy when used alongside a currently used tuberculin skin test.

And most importantly, TB can be ruled out with 48 hours.

Existing tests can take up to several weeks, the researchers said.

Ruling out TB more quickly allows doctors to get on with looking for other explanations for patients' symptoms.

Immune response

The ELISpot-Plus test works by detecting signs of an immune response specific to TB infection.

It checks for a type of protein known as interferon-Y.

On its own, the tuberculin skin test commonly gives falsely positive results if a patient has previously been vaccinated against TB.

But the new test only picks out the immune cells present due to TB infection and not those induced by vaccination.

Patients with a positive result would need further testing to assess whether they have a dormant or active form of the disease.

The current "gold-standard" test requires growing TB bacteria in the laboratory from sputum samples.

Patients being tested need to stay in hospital for three days, undergoing invasive procedures, to obtain necessary samples.

Professor Ajit Lalvani, who led the study team, said the new test could "revolutionise" the way people with suspected TB are managed.

"At the moment, it can take quite a long time to figure out whether or not a patient has the disease, because it can mimic many different conditions and present in many different ways."

The test, which has been trialled in 389 patients in the UK, is not yet licensed but the researchers hope it can be commercially produced at a price which would make it useful in developing countries as well as the NHS.

Dr John Moore-Gillon, vice president of the British Lung Foundation said: "A quicker and earlier diagnosis of TB is a positive step in tackling a disease which is an increasing problem in this country.

"TB has been much ignored so we welcome the greater efforts now being devoted to research into this disease."