Rethinking Healthcare

At-home test checks your spit for TB

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A probe lights up blue if you're infected. This quick and cheap tool could be used in remote locations where the disease is especially common.

Scientists have developed a new fluorescent probe that can be used to quickly detect tuberculosis bacteria from a sputum sample -- using just a homemade LED box and a camera phone. Nature News reports.

In 2010, TB killed nearly 4,000 people a day, mostly in remote places around the world. Treatments are available, but diagnosis can take several weeks – during this time, patients can transmit the infection. (If a person with active TB goes untreated, that individual will infect up to 15 people a year, on average.)

The most common test for active TB is called the ‘sputum smear microscopy.’ That’s when your coughed-up saliva and mucus are examined under a microscope for the presence of TB bacteria (pictured). But this requires a lot of trained staff, and it can’t diagnose TB in children.

And, compared to chest X-rays or blood tests, this fluorescent molecule is a much cheaper and quicker diagnostic test, one that can be used in places that lack clinical infrastructure.

To create an efficient detection method, Stanford’s Jianghong Rao and colleagues developed a simple fluorescent molecule.

  1. In nature, a TB protein known as BlaC breaks down a particular class of chemicals called β-lactams. Here, the researchers designed their molecule to resemble a β-lactam so that it’s cut in half by BlaC.
  2. This probe is normally colorless, but when it’s cut by BlaC from TB bacteria, it releases a blue fluorescent product.
  3. And that’s detected using a homemade box containing a light-emitting diode and a couple of filters.
  4. The faint light that’s emitted can be captured by a camera phone, making it easy to share with clinicians. No microscope, no lab.

A prototype test is currently being developed by Global BioDiagnostics in Texas, with the product expected to be available by 2015.

The work was published in Nature Chemistry this week.

[Via Nature News]

Image: Mycobacterium tuberculosis / CDC via Wikimedia

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Janet Fang

Contributing Editor

Janet Fang has written for Nature, Discover and the Point Reyes Light. She is currently a lab technician at Lamont-Doherty Earth Observatory. She holds degrees from the University of California, Berkeley and Columbia University. She is based in New York. Follow her on Twitter. Disclosure