TBSURE: An Improved Multiplex Real-Time PCR for TB Detection and Differentiation from Nontuberculous Mycobacterial Diseases in Adult Indian Population

Abstract

Background: Tuberculosis (TB), an infectious disease caused by bacterium Mycobacterium tuberculosis, has crossed the borders of developing nations and has now emerged as disease of global emergency due to an alarming increase in cases of co-infection with human immunodeficiency virus (HIV). Conventional diagnostics used for TB diagnosis like microscopy and culture although reliable are time consuming. Rapid diagnosis of the disease is required for early commencement of treatment of TB patients. The diagnosis of extra pulmonary tuberculosis (EPTB) is more troublesome due to limited accessibility of infection sites and lack of accurate differentiation from other granulomatous diseases. Currently, WHO advises use of Xpert MTB/RIF assay for EPTB diagnosis, but this assay cannot be used in resource constrained settings prevalent in most of parts of India. Aim: We aimed to develop a multiplex real-time PCR assay which not only detects Mycobacterium tuberculosis complex (MTBC) but also differentiates them from nontuberculous mycobacteria (NTM). Methods: For development and validation of TBSURE, we included 3, 709 EPTB samples from adult Indian patients suspected for TB. TBSURE is a real time PCR diagnostic which uses three Taqman probes based on IS6110, MPB64 and 16S rRNA genes. The sensitivity and specificity of TBSURE was compared with the goldstandard culture test and XpertMTB/RIF assay for TB detection. Results and Conclusion: TBSURE gave a sensitivity of 92% and specificity of 91% as compared to Xpert MTB/RIF assay, when samples from TB suspected individuals were subjected to both the tests. As compared to AFB culture, TBSURE gave a sensitivity of 93.1% and specificity of 96.5%. Thus, TBSURE is an in-house efficient and affordable diagnostic test for EPTB diagnosis.