Objective: This study is aimed to compare the diagnostic performance of two real-time polymerase chain reaction (PCR) systems for detecting Mycobacterium tuberculosis in clinical samples.

Materials and Methods: Total of 50 clinical specimens sent for the diagnosis of tuberculosis to Mycobacteriology Laboratory of Erciyes University, Medical Faculty, were included in the study. Twenty-five of the culture positive samples were defined as Mycobacterium tuberculosis complex (MTBC) and 7 as non-tuberculous mycobacteria (TDM). Susceptibility tests were performed with BACTEC MGIT 960 system. Mycobacterium tuberculosis real-time PCR; artus^® M. tuberculosis RG PCR Kit (Qiagen, Hilden, Germany) (artus^® RTUS MTB-PCR and GeneXpert MTB/RIF (Cepheid, Sunnyvale, CA, USA) assay systems were used for the molecular diagnosis of the 50 clinical samples.

Results: The results of the both of the molecular diagnostic systems tested revealed that 58% of the clinical samples were MTBC positive, and 42% were negative. When culture was considered as the gold standard; sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of artus^® MTB-PCR and GeneXpert MTB/RIF were found to be 72% vs 96%, 56% vs 80%, 62% vs 82%, 66% vs 95%, respectively. There was no significant statistical difference between the results of GeneXpert MTB/RIF and artus® MTB-PCR (p>0.05). The compliance of the two systems was accetable (kappa=0.507; p<0.05). In this study for the 20 pulmonary and 30 non-pulmonary specimens, the compatibility between culture and artus® MTB-PCR, and GeneXpert MTB/RIF was found to be 75% and 95%, 56.6% and 83.3%, respectively. One clinical sample which was found to be sensitive to rifampicin by BACTEC MGIT 960 SIRE tests, could not be detected by GeneXpert MTB/RIF test.

Conclusion: The results of this study revealed that GeneXpert MTB/RIF can be reliably used in routine laboratories due to its high susceptibility, specificity and ability to give results in a short time. However, more research with high number of clinical samples are required for the validation of the system in routine use.