Is the pleural fluid transudate or exudate?
GROUND: Pleural effusions are classified into transudates and exudates based on criteria developed in the 1970s. However, their accuracy has not been evaluated. We compared the performance of the pleural fluid absolute lactic dehydrogenase level (FLDH), fluid to serum ratio of LDH (LDHR), and fluid to serum ratio of total protein (TPR). TPR has been used instead of the absolute value of fluid protein based on the observation that fluid protein is influenced by changes in the serum protein concentration. However, the rationale for using LDHR remains unexplored. METHODS: Of 212 consecutive patients with pleural effusions, four with multiple causes and eight with an uncertain diagnosis were excluded. ROC curves were generated using sensitivity and 1-specificity values for TPR, FLDH, and LDHR and positive likelihood ratios (LR+ve) were computed using the optimum cut off values. The correlation between pleural fluid and serum concentrations of total protein and LDH was also estimated. RESUL
