Combined uric acid and cholesterol pleural fluid levels as biochemical markers for differentiation between transudative and exudative pleural effusions

Background: Pleural effusion results from an abnormal pathophysiological state of the equilibrium between pleural fluid formation and removal. Normally, pleural space contains about 10 ml of fluid on each side. The aim of the work: To assess the sensitivity and specificity of combined pleural fluid uric acid and cholesterol level in differentiation between the transudative and exudative pleural effusions.Materials and Methods: 54 patients with pleural effusion were included and divided into transudates, and exudates based on clinical, pathological, imaging and Light’s criteria. In addition, uric acid and cholesterol levels in pleural fluid were measured.Results: This study's mean pleural fluid cholesterol level was 90.97 ± 38.51 and 35 ± 5.63 mg/dl in exudates and transudates, respectively. They are statistically significant with sensitivity and specificity were 88% and 100%, respectively. The mean pleural fluid uric acid level in exudates and transudates was 4.08 ± 1.83 mg/dl and 5.86 ± 0.86 mg/dl, respectively and they are statistically significant. The optimum cut-off level for pleural fluid uric acid was 5.15 mg/dl with a sensitivity of 85% and specificity of 80%. The combined parameter of uric acid and cholesterol level in the pleural fluid gives a more powerful discriminating agent between exudative and transudative pleural fluids with sensitivity and specificity being 94.1% and 100%, respectively.Conclusion: The combined parameter of the pleural fluid level of uric acid and cholesterol is of great value for distinguishing between transudative and exudative types of pleural effusions.