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Cases of tuberculosis in the United States are still rare enough to make news. This week, 42 inmates at the Brunswick County jail in North Carolina tested positive for the bacteria, and two years ago the country was captivated by the case of an Atlanta man with a rare form of the disease who had fled authorities and was eventually jailed.
In the developing world, tuberculosis is a much more common killer. There are 9 million cases of TB worldwide every year, and 2 million of those prove fatal.
“If we want to help people in other parts of the world, we have to do something about this. And from a purely self-interested perspective, globalization means that more cases of TB will be coming here,” said Jose Trevejo.
Trevejo, a principal scientist at the Charles Stark Draper Laboratory Inc. in Cambridge, is looking for a new and better way to screen for the disease. His handheld device, which is at least five years away from approval, would detect the “smell” of the gases, called metabolites, coming off the sputum of a patient. A dime-sized sensor would then determine whether the smell indicates tuberculosis.
The preliminary version of the device would require the patient to cough up a phlegm ball to be tested, and tests would take about 10 minutes. But Trevejo envisions a final product that would only require the patient to exhale — like a breathalyzer test for TB. The cost of the device at this stage is projected to be between $1,000 and $2,000, and each sample tested would cost about a dollar. The current test costs about $30 for each sample.
“The current screening test for TB is 125 years old. There has been a real dearth of research on TB, despite what a global health scourge it is,” said Carole Mitnick, assistant professor of social medicine at Harvard Medical School.
Sputum smear microscopy, the most commonly used test, only catches 50 percent of tuberculosis cases, according to Mitnick. Another test is more accurate, but it takes eight weeks to receive results. The new breathalyzer-type test, in addition to being much quicker, would be portable. It would not require a patient to return to a clinic to receive a diagnosis. Trevejo said that is key to reducing the spread of the disease in the developing world, where patients often have to travel long distances to see a doctor or nurse.
Trevejo and Mitnick say a challenge for diagnostics is to determine if the TB is of the dreaded drug-resistant type, so that precious time is not wasted by treating a patient with drugs that will not work. Trevejo said there is evidence that the device may be able to distinguish different types of the bacteria, but that it’s too early to know for sure.
Draper is not the only local institution working on this public health problem. Researchers from Harvard Medical and Massachusetts General Hospital are also developing a portable device, using a totally different mechanism. The Harvard device can count very small amounts of bacteria by using a tiny, simplified version of magnetic resonance imaging, or MRI, according to researchers.
Trevejo hopes that tuberculosis will be just the first of many indications for his breath-analysis device. He foresees its use to detect other respiratory illnesses, such as pneumonia.
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