| Thoracentesis should be performed in all patients with more than a minimal pleural effusion unless clinically evident heart failure is present. | C | 5,33 |
| An effusion is exudative if it meets any of the following three criteria: (1) the ratio of pleural fluid protein to serum protein is greater than 0.5, (2) the pleural fluid lactate dehydrogenase (LDH) to serum LDH ratio is greater than 0.6, (3) pleural fluid LDH is greater than two thirds of the upper limit of normal for serum LDH. | C | 1,5,8 |
| The serum-effusion protein or albumin gradients can be used to diagnose the presence of a transudate after diuresis. | C | 1,9,10 |
| In a lymphocyte-predominant exudate, a pleural fluid adenosine deaminase greater than 40 U per L (667 nkat per L) indicates that the most likely diagnosis is tuberculosis. | C | 26–28 |
| If malignancy is a concern and cytologic examination is nondiagnostic, thoracoscopy should be considered. | C | 5,39,40 |