Role of GeneXpert in diagnosing tuberculous pleural effusion compared with thoracoscopic pleural biopsy

Abstract

Background Pleural effusion caused by tuberculosis (TB) is a common form of extrapulmonary TB. It is usually cause by delayed hypersensitivity to antigens of tubercle bacilli in pleura. It is found that it occurs more in patients with HIV. Aim To evaluate the role of GeneXpert in diagnosing tuberculous pleural effusion compared with thoracoscopic pleural biopsy. Patients and methods This cross-sectional study was conducted on 71 patients with undiagnosed exudative pleural effusion, highly suspected to be tuberculous (as regarding our inclusive criteria). Tuberculin skin test, sputum Ziehl–Neelsen, thoracocentesis, GeneXpert examination, and pleural biopsy via thoracoscopy were done. Results Pleural fluid in most cases was rich in lymphocytes, and adenosine deaminase level (mean+SD) was 24.01±9.9. GeneXpert for 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 confirmed by histological examination of pleural tissue. Overall, 88.73% of the patients were diagnosed by histopathology. The sensitivity of GeneXpert was 22.2%, specificity was 75%, positive predictive value was 87.50%, negative predictive value was10.90%, and finally, its accuracy in evaluating TB pleurisy was very weak (28.6%). Conclusion With high suspicion of TB, 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 GeneXpert has a good role in testing pleural TB.

Keywords

• genexpert
• thoracoscopic pleural biopsy
• tuberculous pleural effusion