Evaluating the Diagnostic Performance of PCR Targeting Insertion Sequence (IS6110) for the Detection of Extra-pulmonary Tuberculosis

The diagnosis of extra-pulmonary tuberculosis remains a challenge to control tuberculosis even though remarkable progress has been made in diagnostics during the last decade. The polymerase chain reaction (PCR) was used in the diagnosis of definitive extra pulmonary tuberculosis patients and to assess the performance of insertion sequence (IS) 6110-based PCR assay as compared to conventional liquid culture by Microbial Growth Indicator Tube (MGIT) 960 system. Patients with clinically suspected extra-pulmonary TB provided 792 clinical specimens. There were 22 ascetic fluids, 69 pleural fluids, 240 cerebrospinal fluids (CSF), 386 endometrial tissues, 47 lymph nodes, 22 pus samples, 1 synovial fluid, 1 fallopian tube, 2 brain abscess, and 2 ovarian cyst samples among the collections. All of these clinical samples were cultured on MGIT 960 tubes containing Modified Middlebrooks 7H9 broth medium and Auramine O staining (FM) for acid-fast bacilli (AFB). The Mycobacterium TB insertion sequence IS6110's 123 bp fragment was the target of the PCR. In our analysis of 792 samples, we found that they were 87.5% sensitive to endometrial samples, 92.31% sensitive to cerebrospinal fluid, 66.66% sensitive to pleural fluid, and 60% sensitive to lymph node samples. Calculations show that the PCR IS6110 has a combined sensitivity and specificity of 85.71% and 82.91%, respectively. It is concluded that PCR using IS6110 primer picked up more positivity in extra-pulmonary samples compared to the conventional culture method for detecting M. tuberculosis.