Study of pleural fluid to serum cholinesterase ratio to differentiate between transudative and exudative pleural effusions

Pleural effusion is an excessive accumulation of fluid in the pleural space. However the etiology remains unclear in nearly 20% of the cases. For the management of the patient, it is important to distinguish exudative pleural effusion from transudative. In 1972, Light et al formulated criteria for differentiating between transudates and exudates, which have been widely accepted. However several reports have shown that Light et al, criteria misclassify a large number of effusions. Therefore several alternative parameters have been proposed.

A hospital based prospective study, 50 patients fulfilling the inclusion and exclusion criteria were studied. Complete history and examination followed by pleural fluid analysis for cell type, cell count, ADA, LDH protein, cholinesterase was done. Routine blood examination including serum cholinesterase was done. The pleural fluid to serum cholinesterase ratioefficacy was compared to Light's criteria in differentiating transudate from exudative pleural effusion.

In the present study the sensitivity of pleural fluid to serum cholinesterase ratio is 95%, while that of Light's criteria is 92.5%. The efficacy in the present study is 94% while that of Light's is 90%.

Sensitivity and accuracy of pleural fluid to serum cholinesterase ratio as a diagnostic parameter to differentiate transudate and exudates is higher than Lights criteria. It is better test compared to all other parameters used in the study.