Polymerase chain reaction (PCR): Its comparison with conventional techniques for diagnosis of extra-pulmonary tubercular diseases

65 clinical samples, which included 5 pus, 4 ascitic fluid and 38 specimens of different tissues, from 57 patients with clinical suspicion of extra-pulmonary tuberculosis were studied for AFB staining, culture for M. tuberculosis, histopathology and PCR. The study was aimed at the detection of M. tuberculosis DNA with the help of PCR in extra-pulmonary tubercular disease in its earliest stage and to compare its efficacy with other conventional diagnostic techniques. On comparing, in 9 fluid samples, only 11.1% were AFB positive, 33.3% were culture positive, 44.4% were cytologically positive and 100% were positive by PCR. In 38 samples from different tissues, 15.8% were AFB stain positive, 92.1% were histologically positive and 97.36% were PCR positive. The overall sensitivity, specificity, positive predictive value and negative predictive value of PCR were 97.87%, 100%, 100%, and 94.73% respectively. It was concluded that maximum sensitivity and specificity can be achieved by the combined use of clinical diagnosis, histopathology and PCR. PCR has a potentially important role in improving the diagnostic accuracy of extra-pulmonary tuberculosis.

Keywords
Extra pulmonary tuberculosis, AFB stain, culture for M.Tuberculosis, histopathology, Polymerase chain reaction