Article review Rapid Molecular Detection of Tuberculosis and Rifampin Resistance [MTB-RIF test] Catharina C. Boehme, M.D., Pamela Nabeta, M.D., Doris Hillemann, Ph.D., Mark P. Nicol, Ph.D., Shubhada Shenai, Ph.D., Fiorella Krapp, M.D., Jenny Allen, B.Tech., Rasim Tahirli, M.D., Robert Blakemore, B.S., Roxana Rustomjee, M.D., Ph.D., Ana Milovic, M.S., Martin Jones, Ph.D., Sean M. O’Brien, Ph.D., David H. Persing, M.D., Ph.D., Sabine Ruesch-Gerdes, M.D., Eduardo Gotuzzo, M.D., Camilla Rodrigues, M.D., David Alland, M.D., and Mark D. Perkins, M.D September 1, 2010, at NEJM.org.. R3 Jo Uk / Prof. Park Myung-Jae

Introduction MDR Tbc (multidrug- resistant tuberculosis) : 500,000 patients Tbc coinfected with HIV : 1.37 million patients (worldwide each year) –Only a small fraction have access to sufficiently sensitive case detection or drug-susceptibility testing. –High frequency of AFB smear (-) in HIV-associated tuberculosis  Diagnostic delay is common. Failure of quick diagnosis and treatment –increased mortality –secondary resistance (including extensively drug-resistant tuberculosis) –ongoing transmission Mycobacterial culture and current nucleic acid–amplification technologies for the detection of tuberculosis and MDR Tbc –Complex / need the associated infrastructure –restrict the use of such tests to reference laboratories.  urgent need for simple and rapid diagnostic tools

Xpert MTB/RIF –fully automated molecular test for Mycobacterium tuberculosis (MTB) and resistance to rifampin (RIF) –heminested real-time PCR assay  amplify an MTB specific sequence of the rpoB gene, which is probed with molecular beacons for mutations within the rifampin-resistance determining region –Process of Xpert MTB/RIF addition of a bactericidal buffer to sputum  The only manual stepaddition of a bactericidal buffer to sputum  The only manual step Transfer defined volume to the MTB/RIF cartridgeTransfer defined volume to the MTB/RIF cartridge cartridge is then inserted into the GeneXpert devicecartridge is then inserted into the GeneXpert device  provides results within 2 hours.

Process of Xpert MTB/RIF test The only manual step

Purpose determine its sensitivity and specificity in the intended target population as compared with the best available reference standard. (by Multicenter, prospective evaluation)

Methods Study Population –July 2008 ~ March 2009 in Peru / Azerbaijan / South Africa / India –consecutive adults with symptoms of pul, Tbc or MDR Tbc.  provide 3 sputum samples each ( >1.5 ml ) 2 specimen – processed with N-acetyl-l-cysteine /sodium hydroxide before microscopy, solid and liquid culture, MTB/RIF test2 specimen – processed with N-acetyl-l-cysteine /sodium hydroxide before microscopy, solid and liquid culture, MTB/RIF test 1 specimen – direct testing with microscopy and MTB/RIF test.1 specimen – direct testing with microscopy and MTB/RIF test.

Methods Categories for Analysis AFB (+) Culture (+) AFB (-) Culture (+) AFB (-) Culture (-) AFB (-) Culture (-) No Tbc Clinical Tbc MTB/RIF test

RESULTS

Final diagnostic categories

Sensitivity and specificity

Detection of MDR Tbc

Conclusion The MTB/RIF test provided sensitive detection of tuberculosis and rifampin resistance directly from untreated sputum in less than 2 hours with minimal hands-on time