Extra pulmonary tuberculosis: a diagnostic dilemma.

Tuberculosis remains a major public health problem globally, with India being one of the high burden countries. The common causative agent is Mycobacterium tuberculosis but in developing countries M. bovis is reported as a potential human pathogen. Almost 20% of all reported cases of tuberculosis are of extra pulmonary form of disease. Diagnosis of extra pulmonary tuberculosis (EPTB) is not always possible with conventional methods, due to the long time required and the paucibacillary nature of samples; hence the need of rapid molecular methods. A prospective study was conducted on 300 patients of EPTB over a period of 5 years. These patients were suspected cases of tubercular meningitis, tubercular ascites and tubercular lymphadenitis. Samples analyzed were cerebrospinal fluid, ascitic fluid and lymph node fine needle aspirate. A two step PCR targeting hup B gene was used. Clinical response to anti tubercular therapy (ATT) was taken as positive (gold standard). PCR for hup B gene was positive in 147 samples out of 155 ATT responders. Of these 85.71% were infected with M. tuberculosis, 9.52% with M. bovis alone and 4.76% showed co infection with both M.tb and M. bovis. The sensitivity and specificity of PCR was 90.32 and 94.48% respectively.