Iraqi Postgraduate Medical Journal

Abstract

ABSTRACT:
BACKGROUND :
Earlier and improved tuberculosis (TB) case detection, including smear-negative disease & expanded capacity to diagnose multidrug-resistant tuberculosis (MDR-TB) are global priorities for TB control. The development of the Genexpert of mycobacterium tuberculosis and rifampicin resistance (MTB/RIF) assay for the Genexpert platform was completed in 2009 and is considered an important breakthrough in the fight against tuberculosis (TB). For the first time, a molecular test is simple and robust enough to be introduced outside conventional laboratory settings.
Genexpert MTB/RIF detects M. tuberculosis as well as rifampicin resistance-conferring mutations using three specific primers and five unique molecular probes to ensure a high degree of specificity. The assay provides results directly from sputum in less than 2 hours. It is commercial real-time polymerase chain reaction (PCR) assay (Xpert™ MTB/RIF).
OBJECTIVE:
To assess the accuracy of the Cepheid Xpert™ MTB/RIF in the detection of M. tuberculosis from respiratory samples in the setting of data collected from TB center in Medical city complex.
MATERIALS& METHODS:
This is primarily laboratory -based study, used stored data from a previously reported retrospective evaluation of 56 patients suspected of having TB from clinical point of view.
9 patients subjected to the examination of sputum & broncoalevoaler lavage (BAL) at the same time rendering the total specimen number about 65 specimens. The results of Genexpert & RIF sensitivity for each patient were discussed &compared with that of direct AFB smear & culture of sputum and broncoalevoaler lavage (BAL).
RESULTS:
The result s of Gene xpert was compared with direct smear microscopically examination which considered as a primary diagnostic test although the highly sensitivity of Genexpert in diagnosing viable tubercle bacilli ,additionally it diagnose the the non-viable one with the same efficiency, such a feature considered an Achilles tendon of this test.The study revealed high sensitivity& extraordinary specificity in diagnosing TB making this technology the most rapid,simple&accurate diagnostic test of TB .
CONCLUSION:
The results demonstrate that rifampin-resistant M. tuberculosis can be detected in DNA isolated from sputum samples in a single-tube assay that takes less than 3 h to perform; the assay is extremely specific and extraordinarily sensitive.
More over the assay is simple to perform and readily automatable for high-throughput screening.