TB blood tests give wrong responses about half the time in poor countries where the disease runs rampant [EPA]

The United Nations health agency has denounced widely used tests to detect tuberculosis as "dangerous" because they are unreliable and can often produce wrong results.

The UN's World Health Organisation (WHO) said on Wednesday it is preparing to recommend against utilising the tests for the infectious lung disease that affects some 14 million people worldwide. As much as one-third of the world's population is thought to harbor the bacteria that cause TB.

"The tests are not reliable and a waste of money and time, putting proper care at risk," Mario Raviglione, the director of WHO's Stop TB department, said.

The test kits, WHO officials said on Wednesday, are largely produced by Western companies and exported to poor countries before they have passed regulatory standards.

A year-long review of the procedures showed that at least half of the tests gave false positive or false negative results, according to the WHO.

"They put patients’ lives in danger," Raviglione told the Associated Press news agency.

The announcement, which is set to be released later this week, will mark the first time that the WHO has issued a "negative" policy  counseling against the use of a particular method for diagnosing a disease.

At least two million of the tests are carried out each year in 17 nations, including China and India, almost exclusively by doctors and health workers in the private or semi-private sector, according to the WHO.

"The WHO is urging countries to ban the inaccurate and unproved blood tests and instead rely on accurate microbiological or molecular tests, as recommended by the WHO," a statement from the agency said.

'Sub-standard tests'

Karin Weyer, a WHO TB specialist, said the investigation into the tests had been requested by the Indian government.

The tests "are often targeted at countries with weak regulatory mechanisms for diagnostics, where questionable marketing incentives can override the interests of patients", Weyer said.

She said that the WHO had never recommended their use.

"It is a multi-million dollar business centred on selling sub-standard tests with unreliable results."

Most of the tests were manufactured in Europe and North America, including France, Italy, Germany, the Netherlands and the US, "even though the blood tests are not approved by any regulatory body", the WHO statement said.

The WHO warning, which has already been passed on to several governments, is the first time it has issued an explicit "negative" policy recommendation against a test for tuberculosis, a disease which kills 1.7 million people each year.

The tests, of which there are at least 18 available on the market, "must be stopped immediately and everywhere", Raviglione said.

Source: Agencies