Role of Polymerase Chain Reaction in diagnosis of Tuberculosis as compared to routine tests

Abstract

Introduction: There is a need for rapid and sensitive detection of Mycobacterium tuberculosis in clinical samples. A study was conducted in which the target for the amplification being a segment of IS6110 in the M. tuberculosis chromosome was evaluated using real time PCR and its results were compared with routine tests, using pulmonary and extra-pulmonary specimen.
 Methods: In this descriptive cross-sectional retrospective study, specificity and sensitivity of PCR were analyzed. A total of 293 clinical samples were processed at a tertiary care hospital of Peshawar, during the time period of 2016-2018, from patients suspected of having pulmonary and extra-pulmonary tuberculosis and Follow up patients with DOTS treatment and MDR treatment that are referred by tertiary hospital were also included in this study after taking their informed consent. Patients not willing to participate in the study were excluded. For identification specimens were stained by Ziehl Neelsen staining (ZN), cultured on Lowenstein–Jensen (LJ) medium and then confirmed by PCR for the detection of Mycobacterium tuberculosis (MTB).
 Results: Of the 293 samples, 165(56.3%) were from males and 128(43.7%) females. Mean age was 44 years (2-85 years). Specimen types included: CSF (30.4%), pleural fluid (4.1%), sputum (15%), urine (2.4%), synovial fluid (2.4%), other fluids (33.1%) and biopsies (12.6%). Only 3.1% of specimens were ZN-smear positive for (MTB). LJ culture identified 7.2% whereas PCR method detected (MTB) in 15% of the total specimens. Using PCR as gold standard, ZN microscopy correctly identified 20.5% of total (MTB) positive specimens and LJ culture detected 47.7%.Specimen types showed significant association with PCR test: 42.9% of synovial fluid samples and 41.7% of pleural fluid samples; 28.6% of urine samples were positive for (MTB) by PCR method. This indicates that PCR analysis of these specimens’ exhibit greater positivity rates for (MTB) as opposed to CSF and other fluids and biopsies
 Conclusions: TB PCR is a rapid and reliable test in the diagnosis and management of tuberculosis.