According to a World Health Organization (WHO) warning Sunday, the widely used blood tests to detect tuberculosis (TB) are “dangerous” to patients because they are unreliable and can produce incorrect results. The WHO announced that it will issue an unprecedented recommendation against using such tests for the infectious lung disease that affects some 14 million people worldwide. As much as a third of the world's population is thought to harbor the bacteria that cause TB.
Mario Raviglione, the director of WHO's Stop TB department said, “The tests are not reliable and a waste of money and time, putting proper care at risk.” He explained that a review of the tests has shown that they produce too many false negative and false positive. Raviglione said the blood tests “are in fact dangerous to patients, since some cases will not be detected and some will be called TB when in fact they do not have it.”
Dr Karen Weyer, who is also from the WHO ‘Stop TB’ department, added, “The evidence we reviewed over the past couple of months shows that one in two patients will be wrongly diagnosed, either [as] false negative or false positive. If it's a false negative patients get the all clear when they in fact have TB, the disease continues to spread, and the patients may die. If, on the other hand, it's false positive, patients are put on treatments unnecessarily while the true cause of their disease remains undiagnosed. We would describe this as unethical - and we are making a very strong urge to governments to consider that TB is a threat and the use of these ineffective tests is also a threat.”
The use of TB blood tests is particularly common in developing countries such as India, where an estimated 3 million people are infected with the disease. The Lancet medical journal reported in January that some of the blood testing kits used there are made in developed countries where such tests aren't licensed. They are ordered by doctors who receive greater commissions for the blood tests than for the older and more reliable sputum microscopy method, the journal reported. “Many of these tests are used in the private-for-profit sector, charging poor people who do not understand the lack of value of the test,” Raviglione said. Most of the 18 kits on the market are produced in Europe and North America. The tests work by detecting antibodies or antigens in the blood that are produced in response to the bacterium.
The WHO guidance will be issued later this week. It is the first time that WHO has issued a “negative” policy, specifically counseling against the use of a particular method for diagnosing a disease.
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