Comparison Of Serum-pleural Fluid Albumin Gradient And Alkaline Phosphatase Against Light's Criteria For Distinguishing Transudates From Exudates

Abstract

Background: The delineation of pleural effusions as being either transudate or exudate is the initial and crucial step in the diagnosis of pleural effusions. The aim is to ascertain the role of serum-pleural fluid albumin gradient and pleural fluid alkaline phosphatase in segregating the exudative and transudative pleural effusions and to compare with the gold standard Lights criteria. Methods: Thirty four patients with pleural effusion admitted over a period of one and half years were studied. Lights criteria, serum-pleural fluid albumin gradient and pleural fluid alkaline phosphatase were used to separate transudates and exudates. Results: According to the Lights criteria, there were 23 exudates and 11 transudates. Out of the 23 exudates, 5 exudates were found to be transudates and among the 11 transudates, 5 cases were found to be exudates by serumpleural fluid albumin gradient (cut off value 1.2g/dL). With pleural fluid alkaline phosphatase 7 cases were classified as exudate and 27 cases were classified as transudates. All the 7 exudates were correctly classified with respect to the Lights criteria. Pleural fluid alkaline phosphatase is 54% sensitive and 78% specific with respect to the Lights criteria for differentiating exudative and transudative effusions. At the cut off value of 75 U/L, the pleural fluid alkaline phosphatase is 34% sensitive but 100% specific for classifying exudates. Conclusion: In conclusion, though lights criteria is mostly recommended, coalesced use of other criteria like albumin gradient and alkaline phosphatase improve the diagnostic confidence in distinguishing exudates and transudates.