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New TB blood test


A new blood test could help the global fight against Mycobacterium tuberculosis Pic: New York State Health Department

A new blood test for tuberculosis (TB) may enable doctors to identify infected people before they develop the active form of the disease.

TB is caused by a bacterium which traditionally attacks the lungs, but can also cause inflammation in other body parts, including the lymph nodes. Diagnosis and preventative treatment of people with early infection is a crucial element of controlling the disease, which is undergoing a resurgence in many countries.

But the current skin test for diagnosing early infections can give false positive results in people vaccinated against TB or exposed to related environmental bacteria.

Now British researchers have developed a test which can detect immune cells responding specifically to the TB microbe. The test is more reliable than the skin test and does not react with strains used in the TB vaccine.

Dr Ajit Lalvani from Oxford University said larger follow-up studies were needed but that there was potential to identify both recently-infected people and others at high risk of TB infection in low prevalence countries.

His team's work is reported in today's issue of the medical journal, The Lancet.

In Australia, the incidence of TB is considered low and stable but drug resistant strains are on the increase. High rates in nearby Asian countries are also seen as a threat to Australian infection rates, which are rising among migrant populations.

The most common way to catch TB is by spending a lot of time indoors with somebody who has the disease. The bacterium cannot be spread to others by dishes, drinking glasses or other objects.

Anyone can have TB bacteria in their body and not even know it. Medical treatment at this stage can prevent the active form of the disease, when the bacteria multiply. This usually happens when the body is weakened from fighting off other infections or diseases, such as HIV, pneumonia or cancer.

A person with TB disease has symptoms of illness which may include a cough, tiredness, weakness, fever, weight loss and coughing up blood.