Pleural effusions occur in a great variety of abnormalities. Even exhaustive diagnostic tests fail to reveal their etiology in as many as 20 percent of leases. Their traditional classification as transudates jr exudates is still useful because it indicates the physiopathologic mechanisms involved: pleural exudates are secondary to alteration of capillary permea-3ility or lymphatic drainage, whereas pleural transu-lates are due either to alteration of hydrostatic and/or x)lloidosmotic pressure in pleural capillaries, or to Suid passing from the peritoneal cavity to the pleural cavity via defects in diaphragm or lymph vessels. Light et al characterized pleural exudates as having pleural LDH (PLDH) >200IU, a pleural LDH/serum LDH ratio (P/SLDH) ^0.6, and a pleural protein/ ierum protein ratio (P/SPROT) ^0.5. In their series, ill but one exudate had at least one of these three characteristics, whereas only one transudate had any jf the three.
Recent research has suggested that pleural choles-:erol level (PCHOL) reflects the etiology of pleural effusions. In the work reported herein, we aimed to /alidate the use of PCHOL and the pleural cholesterol/ ierum cholesterol ratio (P/SCHOL) for differentiating Detween transudates and exudates in pleuritis cases;>f diverse etiology, and to compare the diagnostic efficacy of these parameters with the parameters of Light et al.