2004 SwissTB Award
Dr. Andreas Diacon
Tuberculous (TB) pleurisy is due to infection of the pleural space with TB bacteria. This causes inflammation and accumulation of fluid around the lung. Patients suffer from dyspnoea, cough, malaise and chest discomfort. This condition is frequent where this study was carried out. It remains difficult to diagnose, however, because both sputum and pleural fluid samples rarely contain TB bacteria and because other diseases can present with quite the same symptoms and signs. Several tests for establishing the diagnosis of TB pleurisy are available to date, of which thoracoscopy is the most accurate yet most expensive. Thoracoscopy is a minor surgical procedure during which all fluid is removed, the pleural cavity is inspected and samples are taken under visual control. Pleural biopsies often produce positive bacterial cultures that can be used for antibiotic resistance testing. More recently, novel and relatively low-cost biochemical tests on pleural fluid have been developed, but not directly compared to thoracoscopy. Adenosine deaminase activity (ADA) in pleural fluid is such a test. Many regions with a high incidence of TB also suffer from limited financial resources and are in need of an affordable diagnostic strategy for pleural effusions of unknown origin. The goal of this study was to define the best test strategy next to thoracoscopy for the diagnosis of TB pleurisy.
For this purpose we prospectively recruited 51 patients with exudative pleural effusions undiagnosed after a comprehensive clinical workup. The final diagnosis was TB in 42 patients (82%), cancer in 5 (10%), and idiopathic in 4 patients (8%). As expected, thoracoscopy was the best test for TB pleurisy with a yield of 100% (positive culture: 76%). The diagnostic sensitivity of bronchial wash and pleural fluid culture were low (both 7%). The traditional closed (blind) needle biopsy had a yield of 79% (positive culture: 48%). ADA alone was 95% sensitive and 89% specific. ADA combined with the pleural fluid lymphocyte count was 89% sensitive and 100% specific, but the rate of positive cultures was only 7%. The overall best alternative test was a combination of ADA, lymphocyte count and closed needle biopsy, which reached 93% sensitivity, 100% specificity, and yielded 52% of positive cultures.
This study allowed us to propose recommendations for the workup of undiagnosed exudative pleural effusions in a high incidence area for TB. For patients with typical clinical presentation, combined pleural fluid ADA level and cellcount is an accurate first step for the diagnosis of TB pleurisy. If this test is negative in a situation of high clinical suspicion of TB pleurisy, if antibiotic resistance is of concern, or if other possible diagnoses are strongly considered, thoracoscopy is the method of choice. If thoracoscopy is not available, closed needle biopsy should be performed and combined with pleural fluid analysis for ADA, lymphocyte count and mycobacterial culture. This alternative provides a high diagnostic yield and can even be performed in outpatient settings. It can replace thoracoscopy at considerably lower expense in areas with high incidence of TB, which is of particular relevance for resource-poor countries.
Diagnostic tools in tuberculous pleurisy: A direct comparative study
Diacon AH, van de Wal BW, Wyser C, Smedema JP, Bezuidenhout J, Bolliger CT, Walzl G
Departments of Internal Medicine, Anatomical Pathology, and Medical Biochemistry, Tygerberg Academic Hospital, Stellenbosch University, Cape Town, South Africa