Abstract
Background: The diagnostic challenges in extra-pulmonary tuberculosis remain to be addressed even though remarkable progress has been made in the diagnostics of pulmonary tuberculosis during the last decade. Methods: This study was conducted to evaluate the use of polymerase chain reaction (PCR) in 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. Results: A total of 792 clinical specimens were collected from clinically suspected extra pulmonary tuberculosis patients. The specimens included 22 ascitic fluids, 69 pleural fluids, 240 Cerebrospinal fluids (CSF), 386 endometrial tissues, 47 lymph nodes, 22 pus, one synovial fluid, one fallopian tube, two brain abscess and two ovarian cyst samples. All these clinical samples were subjected to Auromine O staining (FM) for acid fast bacilli (AFB) and culture on MGIT 960 tubes containing Modified Middlebrooks 7H9 broth medium. PCR was performed by targeting 123bp fragment of insertion sequence IS6110 of Mycobacterium tuberculosis. Our study of 792 specimens, revealed their 87.5% sensitivity to endometrial samples, 92.31% sensitivity for cerebrospinal fluid, and 66.66% sensitivity in Pleural fluid and 60% sensitivity in Lymph node samples. The combined sensitivity and specificity of the PCR IS6110 was calculated to be 85.71% and 82.91%, respectively. Conclusion: PCR using IS6110 primer was able to pick up more positivity in extra pulmonary samples as compared to conventional culture method for the detection of M. tuberculosis.
Highlights
Tuberculosis has been a foremost global public health problem from times immemorial
The extracted DNA template was used for the amplification using IS6110 insertion sequence primer specific to Mycobacterium tuberculosis complex
The laboratory diagnosis of extra pulmonary tuberculosis is challenging due to the lack of adequate sample amounts or volumes; the paucibacillary nature of the specimens; the distributing of the sample for various diagnostic tests, resulting in nonuniform distribution of microorganisms; the presence of inhibitors that undermine the performance of nucleic acid amplification-based techniques; and the lack of an efficient sample processing technique universally applicable on all types of extra pulmonary samples
Summary
Tuberculosis has been a foremost global public health problem from times immemorial. World Health Organization (WHO) estimates show that globally there are 9.4 million incident cases of TB of which 80% are in 22 countries, with India ranked as the highest burdened country, accounting for one-fifth of the global TB incidence. The global burden of extra pulmonary tuberculosis constitutes about 15 to 20 % of all cases of TB. The annual global incidence of extra pulmonary tuberculosis has been increasing in the last decade due to the changing TB control practices, spread of HIV (human immunodeficiency virus), the population growth and the cure of infectious cases of TB might have resulted in a relative rise of annual extra pulmonary tuberculosis case detection. HIV pandemic further complicates the situation, as extra pulmonary tuberculosis constitutes more than 50 % of all cases of TB in HIV-positive patients. HIV co-infected TB patients often develop extra pulmonary involvement that may progress rapidly unless the infection is diagnosed and they are treated appropriately [3]. The diagnostic challenges in extra-pulmonary tuberculosis remain to be addressed even though remarkable progress has been made in the diagnostics of pulmonary tuberculosis during the last decade
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