Scientists are excited about a new test that can diagnose drug-resistant forms of tuberculosis far more easily and quickly than other currently available tests.

The test could revolutionize TB diagnosis in the developing world, where TB remains one of the major causes of death.

In a study published in the New England Journal of Medicine, researchers report that the new molecular test, called the Xpert MTB/RIF, successfully identified almost all of 1,730 patients with suspected TB and suspected drug-resistant TB. The study found the test was:

• 98.2 per cent sensitive in patients with known TB
• 99.2 per cent specific in patients without TB
• 97.6 percent sensitive in patients with rifampin resistance

What's more, the test achieved these results in less than two hours – a huge improvement over the days to weeks that traditional TB tests take.

For years, the commonly used test for TB, developed 125 years ago, used a "smear" of mucus from a patient, which was then examined under a microscope by a carefully trained technician looking for the TB bacterium.

Testing improved with the development of rapid molecular testing. But such tests aren't able to identify drug-resistant forms of the illness.

Not only is this new molecular test faster and more accurate, it also identifies patients with TB forms resistant to the antibiotics that doctors turn to first for TB: rifampin or rifampicin.

The National Institute of Allergy and Infectious Diseases in the U.S., supported the development of the testing technology, through a partnership with the manufacturer, Cepheid.

The agency notes that finding cheaper ways to rapidly diagnose TB and its drug-resistant forms are urgently needed. That's because TB remains one of the major causes of disability and death worldwide, with an increasing incidence of drug-resistant forms developing.

Study author Dr. Catharina C. Boehme, from FIND, the Foundation for Innovative New Diagnostics in Geneva, Switzerland, says rapid testing of TB could help slow the disease's spread globally.

"Global control of tuberculosis is hampered by slow, insensitive diagnostic methods, particularly for the detection of drug-resistant forms and in patients with human immunodeficiency virus infection," she and colleagues write.

"Early detection is essential to reduce the death rate and interrupt transmission, but the complexity and infrastructure needs of sensitive methods limit their accessibility and effect."

In an accompanying editorial, Dr. Peter M. Small, who runs the TB program at the Bill & Melinda Gates Foundation, and Dr. Madhukar Pai, from McGill University and the Montreal Chest Institute said while the results were encouraging, the high cost of the sophisticated test might limit its use around the world.

But they add that if emerging countries can successfully tackle their own tuberculosis problems, "the elimination of tuberculosis by 2050 might become a reality."