Comparative Evaluation of Several Gene Targets for Designing a Multiplex-PCR for an Early Diagnosis of Extrapulmonary Tuberculosis

PURPOSE Diagnosis of extrapulmonary tuberculosis (EPTB) poses serious challenges. A careful selection of appropriate gene targets is essential for designing a multiplex-polymerase chain reaction (M-PCR) assay. MATERIALS AND METHODS We compared several gene targets of Mycobacterium tuberculosis, including IS6110, devR, and genes encoding MPB-64 (mpb64), 38kDa (pstS1), 65kDa (hsp65), 30kDa (fbpB), ESAT-6 (esat6), and CFP-10 (cfp10) proteins, using PCR assays on 105 EPTB specimens. From these data, we chose the two best gene targets to design an M-PCR. RESULTS Among all gene targets tested, mpb64 showed the highest sensitivity (84% in confirmed cases and 77.5% in clinically suspected cases), followed by IS6110, hsp65, 38kDa, 30kDa, esat6, cfp10, and devR. We used mpb64+IS6110 for designing an M-PCR assay. Our M-PCR assay demonstrated a high sensitivity of 96% in confirmed EPTB cases and 88.75% in clinically suspected EPTB cases with a high specificity of 100%, taking clinical diagnosis as the gold standard. CONCLUSION These M-PCR results along with the clinical findings may facilitate an early diagnosis of EPTB patients and clinical management of disease.