Evaluate “Rifampicin Resistance” as Surrogate Marker for Rapid Detection of MDR-TB Using Real-Time PCR Directly on FNAC Samples of Tuberculous Lymphadenitis.

Background: India has the dubious distinction of having second largest burden of MDR-TB cases in the world. According to WHO, MDR-TB is defined as resistance to isoniazid and rifampicin, the two most important drugs for treatment of TB. “Rifampicin resistance” is recommended as surrogate marker for MDR-TB by WHO, as at least, 90% of all rifampicin-resistant clinical isolates are also found resistant to isoniazid. Localization of genetic alterations in the 81-bp “Rifampicin Resistance-Determining Region” of rpoB gene in 96% of rifampicin resistant strains make it particularly amenable for early detection of MDR-TB by molecular techniques like Real-Time PCR. Aim: Evaluation of “rifamipicin resistance” as surrogate marker for rapid detection of MDR-TB using Real-Time PCR directly on FNAC samples of tuberculous lymphadenitis (TBLN). Materials and Methods: Eighty cases of TBLN undergoing anti-tubercular treatment (ATT) and 10 lymphadenitis cases of non-tuberculous origin (controls) were included in the study. To evaluate “rifamipicin resistance” as surrogate marker for rapid detection of MDR-TB, Real-Time PCR and conventional Drug Susceptible Testing (DST) were carried out. Results: Eighteen samples were identified as MDR-TB cases by DST. Real-Time PCR picked up mutated ropB gene in 17 cases out of these 18 MDR-TB cases. Conclusion: “Rifampicin resistance” is an efficient surrogate marker for timely detection of MDR-TB using rapid, accurate and sensitive molecular technique like Real-Time PCR.

Detection of mycobacterial DNA directly from FNAC samples of tuberculous lymphadenopathy using real-time PCR: A preliminary study.

Background: Fine needle aspiration cytology (FNAC) is most commonly used in first line investigation for tuberculous lymphadenopathy (TBLAP). Real-time polymerase chain reaction (PCR) an extremely versatile technique is being used for diagnosis and follow up of patients with infectious diseases. It can also be used for detecting Mycobacterium tuberculosis (Mtb) DNA in FNAC samples of TBLAP for rapid diagnosis and treatment. Aim: Detection of Mtb DNA on FNAC samples of tuberculous lymphadenopathy using Real-time PCR. Material and Methods: Twelve clinico-cytologically diagnosed TBLAP cases and five controls were included in the study. FNA samples were used for studying morphology, AFB demonstration, culture and for detecting Mtb DNA using Real-time PCR. Results: Mtb DNA was detected in ten cases (83.33 %) by Real-time PCR. ZN stain was positive in eight cases and culture in six cases. Conclusion: Detection of Mtb DNA in FNAC samples using Real-time PCR is a time saving, logical, economical approach over the culture based method.