Could pleural fluid lactate level have an added diagnostic value in para pneumonic effusion?

Background Pleural effusion is the accumulation of fluid in the pleural space, can be classified into transudative and exudative effusion. A parapneumonic effusion is a pleural effusion that forms adjacent to pneumonia. Para pneumonic effusion can be sub-typed into uncomplicated and complicated effusion. The aim of our work was to identify accuracy of pleural fluid lactate level to discriminate transudative from exudative effusion and uncomplicated from complicated parapneumonic effusion. Methods Thoracocentesis was done with subsequent evaluation of pleural fluid PH, protein, LDH, glucose and lactate. Also, gram stain, microbiological cultures, cytological examination was performed. Medical thoracoscopy was done whenever indicated. Results Our study included 52 males and 38 females with mean age 57.14 ± 11.69 years. Transudative effusions were detected in 22 patients (24.4%). Parapneumonic effusions accounted for 39 cases (43.3%), of these 23 cases were uncomplicated and 16 cases were complicated. The median pleural fluid lactate level in exudative effusion was significantly higher than transudative effusion (P value<0.001), in complicated parapneumonic effusion was significantly higher than uncomplicated parapneumonic effusion (P value<0.001). Pleural fluid lactate cut-off value of 2.68 mmol/l or more yielded 97% sensitivity, 90.9% specificity for detection of exudative effusion (Auc 0.968). A cut of value of 6.22 mmol/l had 87.5% sensitivity, 91.3% specificity for detection of complicated parapneumonic effusion. (Auc 0.971). Conclusion The pleural fluid lactate level has a high accuracy to discriminate transudative from exudative pleural effusion and uncomplicated from complicated parapneumonic effusion.