Powerful new tool to diagnose drug-resistant TB
[DURBAN] Clinical trials of a new molecular technique have found it to be effective at quickly identifying multidrug-resistant tuberculosis (MDR-TB) in resource-poor settings.
As a result, the WHO has endorsed the use of the test in all countries with MDR-TB.
South Africa's National Health Laboratory Service and Medical Research Council (MRC), and the Foundation for Innovative Diagnostics (FIND) collaborated to test 30,000 patients suspected to have MDR-TB in South Africa between 2007 and 2008. They used both the rapid test and conventional testing.
They announced the results at the opening of the 2008 South African Tuberculosis conference in Durban this week (1 July).
The test uses polymerase chain reaction (PCR) technology to amplify Mycobacterium tuberculosis DNA and look for genetic mutations that cause resistance to drugs.
It is the first of its kind to be used against TB and the first new tool for TB in 50 years, says Martie van der Walt, acting director of the TB Epidemiology and Intervention Research Unit at the MRC.
The new TB test yielded results on 92 per cent of all samples compared with about three-quarters (77.5 per cent) of samples tested by conventional methods. It takes between eight hours and two days to get a result, compared to six to eight weeks for conventional testing.
Patients who receive appropriate drugs sooner minimise their risk of acquiring additional drug resistance, van der Walt told SciDev.Net. Earlier diagnosis also cuts the chance of infecting others.
Seventeen countries will receive the tests over the next four years through the WHO Stop TB Partnership's Global Drug Facility. FIND and the WHO's Global Laboratory Initiative will help countries build the capacity — such as laboratory equipment and trained staff — to carry out tests based on PCR techniques.
Mario Raviglione, director of the Stop TB Partnership said in a teleconference this week (30 June) that laboratories in Lesotho, where MDR-TB rates are among the highest in the world, would be ready to use the test within three months.
Laboratory technicians in Ethiopia have been trained, and facilities upgraded, and rapid testing is expected to begin by the end of 2008. Technicians in the Democratic Republic of Congo, the Ivory Coast, Kenya, Nigeria and Uganda have also been trained and are using the test on a smaller scale.
The new tests will be phased in from 2009–2011 in Bangladesh, Indonesia Myanmar and Vietnam.
Developed by Hain LifeScience in Germany, and Innogenetics in Belgium, the test has previously been used on a limited scale by researchers and private laboratories in resource-rich countries, said Richard O'Brien, head of product evaluation and demonstration at FIND.
At US$5 per patient, the test halves diagnosis costs — excluding associated infrastructure and laboratory capacity costs necessary for molecular testing. Using the tests will still be cheaper than treating a larger epidemic, according to O'Brien.
The success has rekindled commercial and research interest in creating a test tailored for extremely drug-resistant TB. A prototype should be available later in 2008.