Role of Genexpert in Diagnosis of Tuberculous Pleural Effusion in Comparison with Thoracoscopic Pleural Biopsy

Abstract

Background: pleural effusion caused by tuberculosis is common form of extrapulmonary tuberculosis. It is usually due to delayed hypersensitivity to antigens of tubercle bacilli in pleura. It is found that it occurs more in HIV patients. Aim: Evaluation the role of GeneXpert to diagnose tuberculous pleural effusion compared with thoracoscopic pleural biopsy. Materials and methods: Cross sectional study, proceeded on 71 patients with undiagnosed exudative pleural effusion, highly suspected to be tuberculous (as regarding our inclusive criteria) tuberculin skin test, sputum Ziehl-Nielsen, thoracocentesis, GeneXpert examination, and pleural biopsy via thoracoscopy were done. Results: pleural fluid in the majority of cases was rich in lymphocytes, Adenosine deaminase (ADA) (mean+SD) was 24.01±9.9. GeneX-pert of pleural fluid was negative in 77.46%. The definitive diagnosis is to isolate tubercle bacilli from biological samples; if it is not available diagnosis can be occurred by histological examination of pleural tissue. As well 88.73% of patients diagnosed by histopathology, but the sensitivity of GeneXpert is 22.2%, specificity is 75%, positive predictive value(PPV) is 87.50%, negative predictive value(NPV) is 10.90% and finally its accuracy in evaluating TB pleurisy is very weak (28.6%). Conclusion: With high suspicion of tuberculosis, GeneXpert may be performed first, if it gives positive data it will be definite diagnosis but if it gives negative data patients should be subjected to further investigation and the most confirmatory one is pleural biopsy. GeneXpert may save time for diagnosis. However if negative other confirmatory tests are mandatory. So GeneXspert has a good rule-in test for pleural tuberculosis.