Diagnostic value of pleural cholesterol in differentiating exudative and transudative pleural effusion

Pleural effusions are most commonly classified as transudative or exudative based on Light's criteria which has shown misclassification in 10%-20% of cases. Studies have demonstrated lesser misclassification with pleural fluid cholesterol criteria. Thus, this study aimed to find the diagnostic properties of pleural fluid cholesterol in differentiating the type of effusion.

This cross-sectional study involving 72 patients was undertaken in a tertiary center in Nepal for a duration of 2 years. On the basis of Light's, Heffner's, etiological, and pleural fluid cholesterol criteria, pleural effusion was classified as exudative or transudative. The findings were then evaluated to determine the diagnostic value of each approach in identifying the effusion type and comparing them on the basis of sensitivity, specificity, positive predictive value and negative predictive value.

Pleural fluid cholesterol detected effusion as exudative with sensitivity of 91.94% and specificity of 80.00% against Light's criteria; with a sensitivity of 98.28% and specificity of 85.71% against the etiological diagnosis. Additionally, against the etiological diagnosis, sensitivity of both Light's and Heffner's criteria was 100%; however, specificity was 71.43% and 64.29% respectively, which is far less than that of pleural fluid cholesterol (85.71%). Furthermore, pleural fluid cholesterol was also found to have better results than protein ratio, LDH ratio and pleural fluid protein ratio in determining the type of effusion.

When considering the avoidance of confusing outcomes in equivocal instances and cost effectiveness in developing nations, pleural fluid cholesterol can be one of the most useful alternative diagnostic methods for differentiating between exudative or transudative effusions.