A simple new test for tuberculosis (TB) called microscopic observation drug susceptibility (MODS) is faster, more accurate, and less expensive to perform than current culture-based tests, researchers report. A MODS assay involves examining sputum broth culture specimens under a microscope to detect coils and cords characteristic of TB growth.
To evaluate the test's performance, researchers collected 3,760 sputum samples and tested them with MODS and two gold-standard TB tests: the Lowenstein-Jensen culture and the automated mycobacterial culture. The MODS test was superior on all counts. Sensitivity of detection was 97.8% for MODS, 84% for Lowenstein-Jensen culture, and 89% for automated mycobacterial culture.
The median time to detection of TB was 7 days for MODS, compared with 26 days for the Lowenstein- Jensen culture and 13 days for the automated mycobacterial culture.
By incorporating various anti-TB drugs into the broth, researchers also accurately identified drug-resistant strains. This gives MODS another advantage over other tests: Drug susceptibility can be determined at the same time TB is diagnosed, saving time and costs.
SourceMoore DAJ, et al., Microscopic-observation drug-susceptibility assay for the diagnosis of TB, The New England Journal of Medicine, October 12, 2006.