Online) An Open Access

Abstract

ABSTRACT Tuberculosis is a disease associated with significant morbidity and mortality, more so in a developing nation like India. Most often it remains undiagnosed and therefore untreated. The gold standard for diagnosis of tuberculosis is by microscopic detection of Mycobacterium or its isolation from the specimen. But because of the poor performance of these conventional methods on extrapulmonary specimens, one has to opt for molecular methods like PCR. However, the cost per test and lack of treatment monitoring by PCR are the disadvantages in a developing country like ours. Therefore, a study was done comparing the conventional methods with PCR. It is a retrospective study conducted over a period of one year, in which a total of 114 samples sent for smear, culture & PCR to the microbiology laboratory of a tertiary care hospital in northern India were included. Sample was first concentrated by Petroff's method and then with the concentrate obtained was inoculated on Lowenstein Jensen medium for culture and rest was used to make smear which was stained by Ziehl Neelsen stain. Another sample was sent to Dr. Lal Path Lab for Real Time PCR. Out of 114 samples, 88 (77.2%) were negative for Mycobacterium by all three methods. 26 (22.8%) samples were positive by PCR, out of which 24(92.3%) were extrapulmonary samples and 2 (7.7%) were pulmonary samples. Out of the 2 pulmonary samples, 1(50%) which was positive by PCR was also positive by conventional techniques; rest 25 samples (mainly extrapulmonary) were negative by conventional techniques. Conventional methods of microscopy & culture remain gold standard for diagnosis of pulmonary tuberculosis & monitoring of treatment. However, due to paucity of bacillary load & uneven distribution of bacilli in extrapulmonary samples, one has to count on PCR. In conclusion, molecular methods like PCR work complementary to conventional methods rather than stand alone superior in the field of tuberculosis diagnosis