New TB test could change current treatments

October 11, 2010 7:11:41 PM PDT
For more than a century, even the suspicion of tuberculosis has lead health departments to quarantine patients for weeks at a time. But now an experimental test for TB could change that and it's already being used in the Bay Area.

For patients consulting with doctors at San Francisco's TB Control Clinic -- the worst scenario is often not knowing.

"For a diagnosis of tuberculosis you want to know right away, as soon as possible, because there's a whole series of things that go into motion," San Francisco TB Control Clinic Director Dr. Masae Kawamura said.

Kawamura says patients with suspected cases have often faced weeks of isolation, until test results come back from laboratory cultures and many start precautionary drug treatment in the meantime.

"If you go down that road, and you find out 'oh, it's not TB,' you've wasted all those resources, you've potentially exposed the patient to toxic drugs and all the stigma that comes with tuberculosis," she said.

But now she says those difficult diagnoses are being made in hours rather than months all because of an experimental testing system being used at the clinic.

The test was developed by Sunnyvale-based Cepheid. It uses the company's lab-in-a-cartridge technology, known as gene expert. A patient's sample is placed inside where the system conducts a molecular analysis, reading sequences of DNA.

Cepheid Chief Medical Officer Dr. David Persing says the system is sensitive enough to identify specific drug resistant strains.

"All in, it's about an hour and a half," he said.

The gene expert machine that analyzes the samples starts at about $25,000. They're already being used to test for TB in several third world countries, though the TB application is not yet approved by the FDA for use in the U.S.

"We consider this a breakthrough technology," Kawamura said

Despite the price tag, Kawamura believes the test could save agencies like hers thousands of dollars ? mainly by ruling out TB in patients who may have had nothing more than a suspicious x-ray and saving both the expense of isolating them and preventing unnecessary investigations into nonexistent outbreaks.

"When we look at our suspects, half did not have active TB and a quarter did not need treatment at all," Kawamura said

Cepheid is currently in talks with the FDA about beginning the approval process. In the meantime, the Bill and Melinda Gates Foundation is helping to fund the development and distribution of the TB in developing countries.


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