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WHO bans serological tests for active TB

1 Aug 2011

Patrick Adams

Source: TropIKA.net

Last week, the WHO did something it has never done before. For the first time ever, the UN agency issued an explicit “negative” policy recommendation against a practice used in the care of tuberculosis.

The WHO urged countries to ban the use of currently available commercial blood tests to diagnose active tuberculosis, claiming that tests are unreliable and could lead to incorrect diagnoses, putting millions of lives at risk.

"In the best interests of patients and caregivers in the private and public health sectors, WHO is calling for an end to the use of these serological tests to diagnose tuberculosis," said Dr Mario Raviglione, Director of WHO Stop TB Department. "A blood test for diagnosing active TB disease is bad practice. Test results are inconsistent, imprecise and put patients' lives in danger."

As reported by Reuters, the WHO suggested “in unusually frank terms” that “mainly Western test-kit manufacturers misled their customers in developing countries with unfounded claims about their worth and used ‘perverse financial incentives’ to boost sales.”

The WHO said in a statement that the recommendation comes after a year of rigorous analysis by its own and independent health experts, who uncovered “overwhelming evidence…that the blood tests produced an unacceptable level of wrong results.”

In more than half of all cases, the tests returned false positives or false negatives, said Raviglione, meaning “that tens of thousands of people with TB get no treatment, so they are highly likely to infect many, many others.”

Yet according to the WHO report, manufacturers of the tests have made claims unsupported by published evidence of sensitivity and specificity “usually in excess of 95%.” Those claims are said to appear on the package inserts included with the tests.

Although they have no regulatory approval anywhere, at least two million of the tests are used every year in 17 poorer countries, including India, where an estimated 1.5 million TB commercial tests are performed each year.

The tests “were often targeted at countries with weak regulatory mechanisms for diagnostics, where questionable marketing incentives can override the interests of patients,” Karin Weyer, Stop TB coordinator of diagnostics and laboratory strengthening, told reporters last week. "It is a multi-million dollar business centered on selling sub-standard tests with unreliable results.”

It was TDR-commissioned research that prompted the WHO to issue its warning—two systematic reviews of serological tests in 2007 and a laboratory-based evaluation of 19 commercially available rapid serological tests for TB, published in 2008. These evaluations found that none of the assays were of sufficient quality to replace smear microscopy as a diagnostic.

In 2010, TDR commissioned an update of the systematic reviews. The findings were identical to the 2007 reviews. TDR and the Stop TB Department at WHO co-convened an Expert Group Meeting to review the findings and discuss the implications for policy.

“The expert group endorsed the findings from an updated systematic review since the TDR report in 2008 and essentially concluded that we should proceed with negative policy guidance based on the fact that the performance characteristics of these tests were way below what one would want and also because the quality of the data were so weak and so bad that it warranted a recommendation against the use of these tests”, Karin Weyer told The Lancet.

“We quickly discovered that manufacturers of these commercial serodiagnostics simply change the name of the test frequently and re-market and re-sell the same test under a new brand name," she said.

At the same time, said Weyer, WHO has approached the negative guidance carefully, so as not to discourage future research and innovation.

Comments

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15 Sep 2011 by Antonio Walter Ferreira:

In my point of view the title is not correct and the widespread use of all serological tests for active tuberculosis diagnosis. It is not correct from the scientific point of view. The right way is that WHO ban the use of some commercially rapid tests for the diagnosis of active TB.
In our experience using well-defined sera samples from patients with pulmonary TB, serological methods such as ELISA with recombinant antigens and Western blotting have shown promising results with levels of sensitivity and specificity higher than those required by the WHO. The most importance of these studies is the large amount of positive serological results in serum samples from patients with negative smear microscopy and culture positive which can introduce rapidly treatment of patients avoiding the bacterial spread

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