This week, the World Health Organization (WHO) criticized the use of blood tests not reliable commonly used to diagnose active TB, as well as aggressive marketing used to promote them. The first recommendation "negative" policy, the agency urged countries to ban these serological tests. "They are a waste of time, and they are a waste of money, and most importantly, they have endangered people who suffer from tuberculosis," Mario Raviglione, Director of the Stop TB Department of WHO, has said at a press conference Wednesday.
instead, WHO recommends that countries use standard microscopy or molecular test a new system called GeneXpert.
tests blood used on at least 2 million people a year are wrong 50% of the time, says the wHO, giving either positive or false negative results, both of which are dangerous.
wHO began studying in 05 blood tests after getting questions from governments and doctors who were concerned about their increasing prevalence. the tests are mainly manufactured in Europe and North America, but they are mainly used in countries where regulations is more lax but the burden of TB is the biggest development.
"It is a profitable business. It is a multi-million, which is centered on selling substandard tests with unreliable results, and we feel this must change, "Karin Weyer, Coordinator of TB diagnosis and laboratory strengthening to Stop TB Department of WHO, said at the press conference.
in a 07 assessment, WHO, with UNICEF, the United Nations development Program, and the World Bank concluded that 19 blood tests commercially available were very inaccurate and insensitive. But since then, the use of serological tests for TB has increased, prompting the wHO to make an updated review of proof. the final review, conducted by WHO and then evaluated by a panel of external experts, was delayed until yesterday Weyer said, because after the 07 report, many companies simply changed the names of their products and remarketing, which makes them difficult to track. Moreover, Weyer said, given the powerful nature of their recommendation, "we must ensure that the science behind this policy could be defended at all challenging."
The consequences of these misdiagnoses were significant. when TB is untreated, individuals are not only in danger, but also unknowingly transmit the disease to others. and when people are not properly diagnosed with tuberculosis, the underlying cause disease goes untreated and the unnecessary use of TB drugs contributes to drug resistance.
These blood tests are inaccurate because they are based on the detection of antigen-antibody produced by Mycobacterium tuberculosis (MTB), the organism that causes tuberculosis. the immune response is a poor indicator, however, because different types of actions antigens mycobacteria, and other infections raise similar antibody responses . Accordingly, blood tests may be detecting the presence of other mycobacterial infections; they can also produce false positives when antibodies remain high after the TB levels were treated.
Despite these shortcomings, manufacturers make claims of great accuracy, Weyer said, citing the instructions for a drug that said the test was 100%, although the study included only 10 topics. She also mentioned the reports of doctors who receive economic incentives to manufacturers of these tests.
Since December 2010, WHO approved / RIF test Xpert MTB, a new molecular diagnostics manufactured by Cepheid, a company based in Sunnyvale, California. The test runs on the GeneXpert system, which uses real-time polymerase chain reaction for rapid detection of MTB and rifampicin resistance, identification of patients infected with drug-resistant strains.
"The advantage of GeneXpert is that you can immediately diagnose TB [determine] if TB is drug resistant," says Weyer. It provides results in 2 hours compared to weeks required to establish a diagnosis of the cultivation of traditional TB. Unlike microscopy, instrument size to the coffee machine does not require a laboratory or trained personnel, she said. The downside is that it costs $ 20,000, expensive compared to $ 1,000 for the purchase of a microscope, although the individual test costs are similar. GeneXpert also requires constant and uninterrupted flow of electricity, lack of many developing countries, although Weyer says studies are underway to try to feed the machines with batteries and solar energy.
Several studies published in PLoS Medicine this week concluded that the MTB test / RIF is very effective in the diagnosis of tuberculosis in HIV-infected patients for HIV, which is particularly difficult, because they often have negative smear results because their disseminated or extrapulmonary tuberculosis. One study showed a 45% increase in case detection for patients with HIV using Xpert MTB / RIF test compared to smear microscopy. Last week, in
WHO still hopes a "point of care" diagnosis that will work at the bedside, but for now, Weyer says "there are many basic science still lacks image ".
0 Komentar