On January 31, 2013, The Cochrane Library published a summary of the findings from a systemic review of the effectiveness of a molecular diagnostic test, the Xpert MTB/RIF assay, for diagnosing tuberculosis (TB) and related drug resistance. The test has been was endorsed by the World Health Organization (WHO). The overall conclusion is that the assay is shown to be largely effective, although there are some unanswered remaining issues.

The review collected evidence from 18 cross-sectional randomized studies with 7816 participants. The key finding of the review is confirmation of the high sensitivity and specificity of Xpert MTB/RIF for detecting multidrug-resistant TB (MTB) in culture-positive sputum samples. The ability of Xpert to detect rifampicin resistance accurately was particularly significant for patients with suspected MDR-TB given the obstacles of diagnosing drug resistance using traditional methods.

You can read the full summary here:
http://www.thecochranelibrary.com/details/editorial/4298651/Evidence-supports-TB-test-so-what-now.html

The Cochrane summary also identified five remaining un resolved issues related to TB testing and the potential use of the new assay test:

• Screening—What is the best method for screening, not just diagnosing, TB?
• Location—Will the use of the new assay test work well in peripheral or rural health care centers? 17 of the 18 studies reviewed in this summary were conducted in central locations.
• Rifampicin-resistance—How can TB centers best use the assay tool to detect and manage rifampicin resistance?
• Assay test evaluation—How can public health authorities effectively evaluate this test in routine practice, where access to culture is generally non-existent?
• Cost—What would be overall cost to roll out the new test in an extensive fashion?