PCR as a Diagnostic Tool for
Dr. Ganavalli S Ajantha,
Professor, Department of Microbiology,
SDM College of Medical Sciences & Hospital,
Sattur, Dharwad-580009, Karnataka, India.
Introduction: Extra-Pulmonary Tuberculosis (EPTB) accounts for approximately 40% of the tuberculosis cases. Though it is not communicable, it is a significant cause of morbidity. This study was conducted to know the efficacy of the Polymerase Chain Reaction (PCR) as an additional tool, along with the conventional methods, in the diagnosis of EPTB.
Materials and Methods: Clinical samples were collected from suspected cases of EPTB. The Ziehl-Neelsen staining (ZNS), culture on the Lowenstein-Jensen medium (LJM) and PCR testing with the use of a commercial kit were performed on the homogenized samples.
Results: A total of 182 samples which were received for the molecular diagnosis of EPTB were also tested by ZNS and culture on LJM for the presence of Mycobacterium tuberculosis. Of these, 22 were positive by at least one of the tests which were used. PCR detected the maximum number of cases of EPTB, followed by culture. The results of PCR and the conventional tests were analyzed by using McNemarâ€™s test for the correlated proportions-the exact method of â€˜IBM SPSS Statistics 20â€™. The analysis showed a statistical significance.
Conclusions: Whenever they are feasible, using all the available tests in combination increases the laboratory detection rates of M. tuberculosis from clinical samples. PCR must be included in the diagnostic panel of EPTB.