ABSTRACT

Background: The conventional techniques like smear microscopy and culture suffer from low sensitivity for diagnosis of extra-pulmonary TB (EPTB). Polymerase Chain Reaction (PCR) is presently seen as a promising alternative to conventional techniques. This study evaluates IS6110 sequence based nested PCR (nPCR) for the detection of Mycobacterium tuberculosis (MTB) DNA directly from clinical samples of extra-pulmonary origin.
Material and Methods: A total of 120 extra-pulmonary samples from the patients with history suggestive of tuberculosis were taken. All the samples were processed for Ziehl-Neelsan staining for acid fast bacilli (AFB), culture and PCR with primers targeting 123bp fragment of IS6110 of MTB complex.
Results: A significant difference was seen in the sensitivities of conventional methods and PCR (p<0.05). Out of these 120 samples 14 (11.7%) were positive by smear, culture was positive in 16 (13.3%) samples. Eithersmear or culture positive 18 (15%) and 39 (32.5%) were positive by PCR.
Conclusions: The nPCR assay targeting IS6110 gene sequence is a rapid and sensitive diagnostic technique for detection of M. tuberculosis genome in clinically suspected extra-pulmonary tuberculosis specimens, as compared to the conventional techniques.