Application of enzyme amplified mycobacterial DNA detection in the diagnosis of pulmonary & extra-pulmonary tuberculosis.

ABSTRACT

BACKGROUND & OBJECTIVES: As isolation of Mycobacterium tuberculosis in culture requires a long time, there is a need for simple rapid method for direct detection of M. tuberculosis from clinical specimens. Amplified nucleic acid hybridization assays such as polymerase chain reaction (PCR) have shown promising results. In the present study, the sensitivity of PCR assay was assessed over smear microscopy for rapid diagnosis of tuberculosis in pulmonary and extra-pulmonary samples from patients suspected to have tuberculosis. METHODS: A total of 37 clinical samples from patients with pulmonary tuberculosis and 133 from patients with extra-pulmonary tuberculosis were subjected to Ziehl-Neelsen staining for smear preparation and PCR for detection of mycobacterial DNA. RESULTS: It was observed that 100 per cent of acid fast bacilli (AFB) positive and 35.7 per cent of AFB negative pulmonary samples and 82.76 per cent of AFB positive and 56.73 per cent of AFB negative extra-pulmonary samples were positive for mycobacterial DNA detection. Total positivity rates of DNA amplification method in pulmonary and extra-pulmonary samples were 75.67 per cent and 61.7 per cent respectively which were significantly higher in comparison with AFB positivity, which was 62.16 per cent in pulmonary and 21.8 per cent in extra-pulmonary samples (P < 0.05 and P < 0.001 respectively). INTERPRETATION & CONCLUSION: Routine application of DNA amplification method in diagnosis of AFB negative patients with pulmonary or extra-pulmonary tuberculosis may be a useful tool for detection of M. tuberculosis.