Evaluation Of Biochemical Parameters To Differentiate Transudates From Exudates In Certain Diseases
Anita B. Kale, MD Biochemistry, Associate Professor, Department of Biochemistry, Jawaharlal Nehru Medical College, Sawangi (Meghe), Wardha, Maharashtra.(India)
Background: Pleural effusion is a common occurrence in medicine wards/OPD. To determine the cause of the pleural effusion is not always easy. The distinction between an exudate and a transudate is the first and the most important step in the differential diagnosis of a pleural effusion. Several biochemical markers are used to classify the type of pleural effusion. The oldest and the most conventional way of classifying the pleural effusion is by the Lightâ€™s criteria. There are multiple other biochemical markers which are available, the diagnostic accuracy of which is not well established and is a subject of debate.
Aim: To evaluate the diagnostic performance of the pleural fluid protein, LDH, cholesterol, bilirubin and their ratio with serum values, as well as the albumin gradient in differentiating the pleural fluid into transudate and exudate .
Materials And Methods: A total of 50 cases of pleural effusion due to different diseases were analysed using certain biochemical parameters like pleural fluid cholesterol, protein and LDH. Their ratio with serum values and the albumin gradient were also analysed.
Statistical Analysis: ROC curves were drawn for individual markers and the areas under the curve were computed and compared using the SPSS version 17. The optimal cut off with a combination of highest sensitivity and specificity was defined.
Result: The pleural fluid protein, its ratio to serum protein and pleural fluid LDH had excellent diagnostic accuracy in differentiating exudative pleural effusions from transudative effusions. Pleural fluid LDH levels were not influenced by serum LDH levels. The optimal threshold for pleural fluid LDH was 175 IU/L.
Conclusion: The pleural fluid to serum protein ratio and pleural fluid LDH had excellent diagnostic accuracy in classifying the pleural fluid type. A single test pleural fluid LDH had diagnostic performance higher than or comparable to most of the other biochemical parameters.