Objectives. To study the diagnostic value of pleural fluid cholesterol in differentiating transudative and exudative pleural effusion. To compare pleural fluid cholesterol level for exudates with Light’s criteria. Design. Cross sectional descriptive study. Settings. Medical wards of Tribhuvan University Teaching Hospital. Methods. Sixty two cases of pleural effusion with definite clinical diagnosis admitted in TUTH were taken and classified as transudates (19) and exudates (43). The parameters pleural fluid protein/serum protein ratio (pfP/sP), pleural fluid LDH/ serum LDH ratio, pleural fluid LDH (pfLDH) and pleural fluid cholesterol (pCHOL) were compared with clinical diagnosis with regard to their usefulness for distinguishing between pleural exudates and transudates. Results. The pCHOL values determined were for exudates, for transudates, the differences between the transudates and others are statistically significant ( ). It is seen that pfP/sP ratio has a sensitivity of 81.4% and specificity of 82.6%; pfLDH/sLDH ratio has a sensitivity of 86% and specificity of 94.7% and pCHOL with sensitivity of 97.7% and specificity of 100% for differentiating exudative and transudative PE. Conclusion. The determination of pCHOL is of great value for distinguishing between pleural exudates and transudates and should be included in routine laboratory analysis of pleural effusion. 1. Introduction Light et al. in 1972 found criteria to have sensitivity and specificity of 99% and 98%, respectively, for differentiating transudative and exudative PEs (ratio of protein in pleural fluid and serum >0.5; ratio of LDH in pleural fluid and serum >0.6; pleural fluid LDH >2/3rd of upper limit of serum LDH) [1]. But the other investigators could only reproduce specificities of 70–86% using Light’s criteria. Also it is found that 25% of patients with transudates pleural effusion are mistakenly identified as having exudative effusion by Light’s criteria. In cases of heart failure on diuretic therapy, the transudative PE has high protein [2]. Pleural fluid cholesterol can be used to classify exudates and transudates as it misclassifies fewer cases than any other Light’s parameters [3]. From meta-analysis, Heffner et al. 2002 have identified pleural effusion of exudative type with at least one of the following conditions [4].(i)Pleural fluid protein >2.9？gm/dL. (ii)Pleural fluid cholesterol >45？mg/dL (1.16？mmol/L).(iii)Pleural fluid LDH >2/3rd of upper limit of serum. Pleural cholesterol is thought to be derived from degenerating cells and vascular leakage from increased
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