Evaluation of Nested Polymerase Chain Reaction for the Diagnosis of Pulmonary Tuberculosis.

ABSTRACT

Utility of Polymerase Chain Reaction (PCR) test for diagnosis of pulmonary tuberculosis was evaluated in 50 clinically diagnosed cases. All samples were also processed for microscopy by Ziehl-Neelsen (ZN) staining and culture on Lowenstein-Jensen medium (LJ). PCR was positive in all microscopy and culture positive specimens. There were 11 samples positive by PCR but failed to grow in culture. With respect to culture the sensitivity (SN), specificity (SP), Positive Predictive Value (PPV) and Negative Predictive Value (NPV) of PCR was 100%, 57%, 68% and 100% respectively. The values for PCR on final evaluation taking into consideration clinical, radiological, microbiological evidence and response to antitubercular treatment were SN- 100%, SP-88%, PPV-94% & NPV-100% respectively. PCR detects M. tuberculosis complex with greater sensitivity and should be useful for rapid diagnosis of tuberculosis.