TB diagnosis breakthrough

There are very few options to cure
the deadly XDR-TB strain.
(Image: tballiance.org)

A doctor examines a TB patient.

Several campaigns are currently in place
To educate the public about TB.
(Image: Stoptb.org)

Khanyi Magubane

A new, advanced diagnostic method to detect multi-drug-resistant tuberculosis (TB) will now cut the diagnosis time from two to three months, to just a day or two.

Health Minister Manto Tshabalala-Msimang launched the new diagnosis tool on 1 July 2008 at a four-day TB conference in South Africa.

She says the development of the new diagnostic tool follows a high level Southern African Development Community meeting, hosted by South Africa, where medical researchers were urged to find a quicker way to test for multi-drug-resistant (MDR) and extensively drug-resistant (XDR) TB.

“Successful prevention and treatment of multiple-drug-resistant TB has been undermined by conventional drug susceptibility testing that is prone to difficulties and takes a long time before a diagnosis can be made,” Tshabalala-Msimang said.

The research initiative was conducted in partnership between the World Health Organisation, the Stop TB Partnership, UNITAID and the Foundation for Innovative New Diagnostics. South African partners included the national Department of Health and Medical Research Council.

The new molecular testing method to diagnose MDR-TB, which until now was used only for research purposes in countries including South Africa, will be made available to 16 nations in Africa.

The new method, or line probe assays, involves testing the DNA collected from a swab of a patient’s saliva. An accurate diagnosis can then be made within two days.

This is a marked improvement on the old method. In most developing countries, TB patients would be tested for MDR-TB only after they had failed to respond to standard TB treatments. Even then, this only happened when the health practitioner suspected MDR-TB, and it used to take about two months or more to confirm the diagnosis.

Patients would then have to wait for the test results before they could receive the treatment. During this period they were at risk of spreading the multi-drug-resistant disease to others. Because of the prolonged process in the past, patients often died before results were determined.

Heavy costs involved

The new testing system is not going to come cheap. According to Dr Karin Weyer, team leader for laboratory services at the World Health Organisation, South Africa is expected to start using the method at a cost much higher than initially thought. However, she said it was still cheaper than the current methods used to diagnose MDR-TB and XDR-TB. Weyer added that the quick testing of MDR within one day would accelerate the testing for XDR-TB.

The cost per capita of treating TB patients is generally very heavy, as drug-resistant TB is expensive to treat.

History of TB in South Africa

According to the Health Systems Trust, an organisation supporting health systems development in South Africa, TB arrived in the country with colonialists, settlers and missionaries, many of whom were already infected from the TB epidemic which had swept Europe and North America during the 17th century.

When gold mining started on the Reef (presently Gauteng) in the late 1800s, black migrant workers who came in contact with those infected with the disease contracted it.

By 1930, it was estimated that over 60% of the black population of South Africa was infected. In 1953, 780 per 100 000 of the population of the northern and eastern parts of the country had the disease.

Today, South Africa still has one of the highest TB infection rates in the world. Almost 1 000 South Africans out of every 100 000 are living with the communicable disease.

WHO says treatment success rates in South Africa remain low, with death and default being the most frequent negative outcomes. Although case notification continues to increase, with the 70% case detection rate being reached for the first time in South Africa in 2006, the treatment success rate remains low.

The prevalence of HIV/Aids has also contributed to the high death rate among those with TB.

MDR-TB and XDR-TB explained

Extensively drug-resistant TB is a relatively rare type of MDR-TB. It is resistant to almost all drugs commonly used to treat drug-susceptible or regular TB.

TB can usually be treated with a course of four standard drugs known as first-line drugs. If these are taken or prescribed incorrectly, MDR-TB can develop. However, MDR-TB can be treated with second-line drugs, but these are more expensive and often come with more side effects. The treatment process also takes much longer than for regular TB.

When second-line drugs are prescribed or taken incorrectly, XDR-TB can develop. At this stage there are very few treatment options available.

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