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Rapid TB test: game changer?

March 2011
Kampala, UgandaWant to embed this video?
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With the results coming so quickly, he was still in the hospital and able to start counseling and treatment straight away."
Here at Mulago hospital in the Ugandan capital, Kampala, tuberculosis patients sit idly, waiting for the opportunity to go home in a few days or weeks, where they can continue their treatment.

This for a disease that kills 1.7 million people a year, and is extremely difficult to cure.

Treatment at hospital and in the home usually takes eight months, along with near-daily regimens of powerful medications, to clear the infection.

If a patient develops drug-resistant tuberculosis, MDR-TB, the cost and length of treatment skyrockets.

For developing nations, treating both types of TB is an enormous burden.

Uganda’s National TB Control Manager, Dr. Francis Adateu, says that’s especially true for a country with such a young population. “We have a very high population growth rate that’s standing at 3.2 percent per annum, so every year we are bringing in new fertile ground for TB transmission.”

Compounding the problem for health officials is the length of time it takes to diagnose suspected cases of TB.

Often, sputum samples are sent away to be examined under a microscope – a technology that hasn’t changed for a century. But that doesn’t detect drug-resistant TB. For that, cell cultures must be taken.

It can take up to two months from the day the patient submits a sample to the time that the results come back from the lab. During that period the person could infect many other people.

But at the Mulago Hospital, a new device that’s being hailed as revolutionary in the fight against TB is being used.

It’s a small, nondescript box that packs a big punch by cutting the diagnosis time for TB and MDR-TB to less than two hours.

The GeneXpert achieves this by analyzing the patient’s DNA, looking specifically for genetic sequences that are associated with TB.

All the operator has to do is treat each patient’s sputum sample with chemicals to kill any TB, making it safer to handle, transfer each sample into a special cartridge, then load the cartridges into the GeneXpert, four separate patient samples at a time.

An hour and forty minutes later, the DNA has been tested and the results are in.

Alfred Andama, one of the lab technicians, explains: “The results as you can see in the results column, the first one is ‘MTB detected’ and the rest are ‘MTB not detected.’” he says. “In the assays you find that where the MTB was detected there was no Rifampicin resistance detected.”

One of the four patients tested positive for tuberculosis, but he tested negative for drug-resistance. If he had developed drug resistance, it would have shown clearly on the screen as ‘RIF detected,’ meaning he has resistance to Rifampicin, one of the key TB drugs.

In this case, the patient who tested positive for TB was 36-year old auto mechanic Rashid Wasswa.

With the results coming so quickly, he was still in the hospital and able to start counseling and treatment straight away.

That turnaround time has been hailed as a major milestone in TB control by the World Health Organization, which has endorsed the device.

But one potential drawback is the cost. Even with discounted pricing, each GeneXpert machine is around $17,000. In addition each test costs $17 to run. For developing nations that’s a high price to pay.

But Adateu says it’s not a deal-breaker. “Maybe in the interim we would need help but I think even the ordinary sputum smear microscopy is not as cheap as we were advised. Lifting a lot of slides by air here costs a lot.”

The Swiss-based Foundation for Innovative New Diagnostics, which developed the GeneXpert with an American company, Cepheid, says the price will likely go down over time, like many new technologies.

If that happens, the hope is that DNA testing for TB and other diseases will become mainstream, even in developing nations.
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