Devising an inexpensive, quick tuberculosis test for developing areas

The typical way that physicians screen for TB, which is caused by the bacterium Mycobacterium tuberculosis (Mtb), is with a tuberculin skin test or an examination of a patient's sputum under a microscope. To weed out false positives, a more reliable test that involves growing Mtb cultures can be performed, but that requires weeks to complete. For all of these methods, experienced personnel are needed. Another approach that is both quick and accurate is a nucleic acid amplification test, which makes many copies of the Mtb DNA in a sample. However, it is expensive and requires a lab setting. So, Matt Trau, Nicholas P. West and colleagues set out to create a simple, inexpensive and reliable way to quickly test for TB.

The researchers began with a newly created nucleic acid amplification test that does not require expensive lab equipment to detect Mtb. Still, this modified test typically uses costly fluorescence technology to read the results. So the team substituted the fluorescence detector with a colorimetric assay that changes to a blue hue if the infection is present, allowing health care workers to identify positive test results right away with the naked eye. They demonstrated how the modified diagnostic could be put on cheap, disposable electrochemical sensors for increased sensitivity, even in the field. Because the assay is inexpensive, quick and highly specific for the Mtb bacterium, the researchers say it could have a big impact in low-resource communities.