Coagulation factors and fibrinogen in pleural effusions.

31 pleural effusions from 27 patients with varied diseases were studied for specific coagulation factors and fibrinogen. In all fluids, exudates had a higher content of factors and fibrinogen than transudates. When pleural fluid to plasma total protein ratios were compared to specific coagulation factors a positive correlation existed for all. This was not true for fibrinogen. There was a poor correlation between the molecular weights of the specific factors and fibrinogen and their appearance in the pleural fluid. The concentration of factor XII in 35% and factor XI in 11% of pleural fluid exceeded their respective plasma concentration.