History and Objectives: Due to the prevalence of pleural effusion and the importance of its differential diagnosis and recent reports on the cholesterol levels of the pleural fluid, the present study was carried out in order to assess its diagnostic value in various types of pleural effusion on patients referred to the Shaheed Beheshti hospital in Kashan in 1996-1997.

Materials and Methods: A diagnostic clinical trial was conducted on 85 patients. In a sitting position, pleural fluid aspiration was obtained and cholesterol, lactate dehydrogenase (LDH), protein content and at the same time blood total protein and LDH was obtained. On the basis of light (Golen Standard) characteristics, pleural fluid is categorized as exudate or transudate. Cholesterol levels were determined based on the enzymatic method. Cholesterol levels higher than 42 mg/dl was taken as exudatives and otherwise it is taken as transudative. Hence on the basis of pleural cholesterol four other variables (Sensitivity, specificity, positive and negative predictive values) were determined.

Results: From 85 patients, 36 patients were transudate and the rest (49) were exudates. Sensitivity and specificity of cholesterol were 92 and 89 percent respectively and positive and negative predictive values and usefulness were 92, 89 and 91 percent respectively.

Conclusion: Cholesterol has a high diagnostic value for the differentiation of transudative and exudative pleural effusion. Since cholesterol determination is a simple laboratory procedure, its determination is recommended for patients suffering from pleural effusion.