GeneXpert--a game-changer for tuberculosis control?

Stephen Lawn and colleagues [11] report in this issue of PLoS Medicine that a single MTB/RIF test detected less than half of the cases of smear-negative culture-positive TB in HIV-positive patients being screened for TB to check whether they could safely be provided with chemoprophylaxis. [...]a single MTB/RIF assay may be insufficient for "ruling-out" TB, although a second test for each patient increased sensitivity to 62%. Furthermore, experiences with HIV viral load and CD4 cell counting tests have demonstrated that advocacy can convince donors to fund the rapid implementation of relatively expensive diagnostic technologies when needs and benefits are clear, and the MTB/RIF test may be such a test. [...]costliness may not prevent the roll-out of this test to the limited numbers of TB patients requiring drug resistance testing, but may severely restrict the availability of this assay for the much larger numbers of people needing testing for suspected TB.