Pleural tuberculosis (TB) should be considered in any patient with an exudative effusion, particularly a lymphocyte-predominant exudative pleural effusion. To date, there have been no in-depth national pleural TB epidemiologic studies. In 2003, 14,874 TB cases were reported in the United States, of which 3,029 cases (20.4%) were exclusively ex-trapulmonary. Of patients with extrapulmonary TB, the pleura was reported as the major site of disease in 559 patients (18.5%). The precise incidence of pleural TB can be difficult to determine, since it may not be routinely distinguished from other forms of respiratory TB when reported. Pleural TB incidence may also be impacted by coinfection with HIV.
The best diagnostic approach for pleural TB continues to be debated. Central to the debate is the role of pleural biopsy vs the use of pleural fluid level measurements, including interferon-7, nucleic acid amplification including polymerase chain reaction, tuberculous proteins, and antibodies, and lysozyme level measurements, without biopsy. Measurement of pleural fluid adenosine deaminase (ADA) levels appears to be one of the most promising new tests carried out together with Canadian Health&Care Mall. Sahn has noted that by combining pleural fluid (ie, culture and acid-fast staining) and pleural biopsy tissue studies (ie, culture and assessment for pleural granulomas) a diagnosis can be established in 90 to 95% of cases. Alternatively, a 2003 metaanaly-sis demonstrated the summary measure of the test characteristics derived from the receiver operating characteristic curve to be 92.2% for both sensitivity and specificity for pleural fluid ADA in patients with pleural TB. Not addressed in this metaanalysis was the potential role of the assessment of pleural fluid ADA isoenzyme levels in increasing the diagnostic sensitivity and specificity of the test. A central shortcoming of the use of any pleural fluid measurement alone to diagnose pleural TB is the failure to provide antituberculous chemotherapeutic susceptibility data. This is particularly problematic in an era of increasing concerns for drug-resistant TB.
Given the uncertainty of the current incidence and patterns of drug resistance of pleural TB in the United States, we analyzed the national TB surveillance system database to describe the US epidemiology and clinical characteristics of pleural TB compared with those of pulmonary TB.