has resided in a high TB prevalence country Is continually exposed to populations where TB prevalence is high. These have been reviewed in detail. Adenosine deaminase In 2007, a systematic review of adenosine deaminase by the NHS Health Technology Assessment Programme concluded "There is no evidence to support the use of ADA tests for the diagnosis of pulmonary TB. However, there is considerable evidence to support their use in pleural fluid samples for diagnosis of pleural TB, where sensitivity was very high, and to a slightly lesser extent for TB meningitis. In both pleural TB and TB meningitis, ADA tests had higher sensitivity than any other tests." Nucleic acid amplification tests (NAAT) NAATs for TB are a heterogeneous group of tests that use either the polymerase chain reaction (PCR) technique or transcription-mediated amplification (TMA) or other forms of nucleic acid amplification methods to detect mycobacterial nucleic acid. These tests vary in which nucleic acid sequence they detect and vary in their accuracy. In the decade of the 2000s, the two most common commercially available tests were the amplified mycobacterium tuberculosis direct test (MTD, Gen-Probe) and Amplicor (Roche Diagnostics). In 2007, a systematic review of NAAT by the NHS Health Technology Assessment Programme concluded that "NAAT test accuracy to be far superior when applied to respiratory samples as opposed to other specimens. Although the results were not statistically significant, the AMTD test appears to perform better than other currently available commercial tests." Xpert ® MTB/RIF and Xpert MTB/RIF Ultra has high specificity in diagnosing extrapulmonary tuberculosis and is accurate in detecting rifampicin resistance. However, clinicians should rely on clinical judgement to diagnose TB meningitis when culture results are negative. A 2007 before-after observational study found that use of the MTD test reduces inappropriate tuberculosis therapy. The study found the accuracy of the MTD test as follows: Overall sensitivity 92% specificity 99% Smear positive patients sensitivity 99% specificity 98% Smear negative patients sensitivity 62% specificity 99% In 2010 the Xpert MTB/RIF test, another NAAT for TB, became commercially available and, as the CDC said in 2015, it began "revolutionizing tuberculosis (TB) control by contributing to the rapid diagnosis of TB disease and drug resistance. The test simultaneously detects Mycobacterium tuberculosis complex (MTBC) and resistance to rifampin (RIF) in less than 2 hours. In comparison, standard cultures can take 2 to 6 weeks for MTBC to grow and conventional drug resistance tests can