Clinical characteristics and prognosis of lymphocyte dominant exudative pleural effusion with low ADA, low CEA, negative cytology and negative AFB smear

Background: A pleural effusion is a common medical problem. Despite several diagnostic tests, 15-20% of pleural effusions go undiagnosed. The aim of this study was to evaluate the clinical characteristics and prognosis of a lymphocyte dominant exudative pleural effusion with a low adenosine deaminase (ADA), low carcinoembryonic antigen (CEA), negative cytology and negative acid fast bacilli (AFB) smear. Method: From Jan 2000 to Aug 2001, 43 patients with lymphocyte dominant exudative pleural effusions whose AFB smear and cytologic exam were negative, their pleural fluid ADA level was < 40 IU/L, and their CEA level was < 10 ng/mL were enrolled in this study. A retrospective analysis of the patients' medical records was carried out. Result: Among 31 of the 43 cases (72%), probable underlying diseases causing the pleural effusion were identified: 21cases of malignant diseases, 4 cases of liver cirrhosis, 2 cases of pulmonary tuberculosis, 1 case of end stage renal disease, 1 case of a chylothorax, 1 case of a post CABG (coronary artery bypass graft) state, 1 case of a pulmonary embolism. No clinically suspected etiology was identified in the remaining 12 cases (28%). Of these 12 pleural effusions, 7 cases spontaneously resolved, 2 effusions resolved with antibiotics, and the other 2 cases were persistent. Conclusion: Lymphocyte dominant exudative pleural effusions with a low ADA, low CEA, negative cytological exam, and negative AFB smear, but without a definite cause might have a benign course and clinicians can observe them with attention.