Tuberculosis Diagnostics: Old Foe, New Tools

Tuberculosis (TB) continues to be a major global problem, with an estimated third of the world’s population infected with Mycobacterium tuberculosis (M.tb). The utility of novel and emerging technologies for the diagnosis of TB remains unclear, especially in high burden settings. There is an ongoing search for rapid, inexpensive, easy-to-use, highly sensitive and specific point-of-care tests for TB diagnosis. Furthermore, diagnosing smear negative or sputum-scarce TB, as well as patients co-infected with human immunodeficiency virus, is problematic. Smear microscopy has poor sensitivity, cannot identify drug resistance, and when followed up with culture tests it takes several weeks to obtain a result. Biological samples other than sputum such as blood, urine and bronchoalveolar lavage fluid are thus increasingly being used for diagnostic purposes. However, there is a low yield of rapid diagnostic tools, and the use of recently released commercially available technologies such as the M.tb antigen-specific Interferon Gamma Release Assays (T-SPOT®.TB and QuantiFERON®-TB Gold In-Tube), urine lipoarabinomannan Clearview-TB® ELISA assay and Xpert® MTB/RIF assay, requires clarification.