Comparison of the real-time polymerase chain reaction and xpert Mycobacterium tuberculosis/rifampicin assay for the detection of Mycobacterium tuberculosis

Abstract

Background A serious issue with world health is tuberculosis (TB). Annual estimates from the World Health Organization (WHO) put the number of incident cases at 9.6 million. The aim of this work was to compare between real-time polymerase chain reaction (PCR) and GeneXpert in recognition of Mycobacterium tuberculosis (MTB) with special reference to quantification of MTB and to speed of detection of the organism. Materials and Methods Thirty individuals participated in this prospective clinical quasi-interventional trial with clinical data and chest radiography suggestive of pulmonary tuberculosis. Participants were split into three groups equally: group I (control group) was zielneilsen stain (ZN) stain positive and culture positive, group II were ZN stain negative and culture positive and group III were ZN stain negative and culture negative. Each participant was exposed to a plain chest radiography and a complete blood picture. Results Real-time PCR result was significantly correlated with loss of appetite and weight in group III. There were negative correlations between PCR and mediastinal lymphadenopathy in group I. In group I GeneXpert was significantly correlated with night sweat and fever, breathlessness and cavitary lesion. In group III GeneXpert was significant correlated with site of lesion and night sweat and fever. Conclusions For TB patients, the PCR test is crucial in order to provide prompt diagnosis and therapy. When comparing AdvanSure tuberculous /non tuberculous mycobacterium (TB/NTM) real-time PCR with Xpert MTB/rifampicin (RIF) assay, the latter is more advantageous due to its test-method simplicity and quicker than real-time PCR ability to simultaneously identify rifampin resistance. However, its sensitivity for specimens with an acid-fast bacilli (AFB) smear negative but a positive culture is less than AdvanSure TB/NTM real-time PCR. With special reference to the quantification of MTB, TB/NTM real-time PCR is a quantitative test but Xpert MTB/RIF is semiquanitative.

Keywords

• mycobacterium tuberculosis; real-time polymerase chain reaction; xpert mycobacterium tuberculosis/rifampin assay