WHO: Blood Tests for Tuberculosis Are Unreliable

The World Health Organization said Sunday it will issue guidance against "dangerous" but widely used blood tests to detect TB.

A review of the tests finds they can produce too many false-negative and false-positive results. "The tests are not reliable and a waste of money and time, putting proper care at risk," said Mario Raviglione, director of WHO's Stop TB program. They "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."

The WHO recommendations to be released later this week mark the first time the agency has issued a "negative" policy targeting a particular diagnostic method.

The blood tests are common in developing countries like India, where approximately 3 million people are TB-infected. Worldwide, some 14 million people have the infectious lung disease, and up to a third of the total population is thought to harbor the TB-causing bacteria.

In January, the Lancet reported that some of the blood testing kits are manufactured in developed countries that do not themselves license the tests. Doctors ordering the tests receive a larger commission than they would for ordering the older, more reliable sputum microscopy test, the Lancet said.

"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.

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