Determination of tissue polypeptide-specific antigen in pleural fluid and serum from patients with pleural effusion

As a tool for differentiating malignant and benign pleural effusions, we evaluated the diagnostic value of the assay of tissue polypeptide-specific antigen (TPS) in pleural fluid and serum, and of the pleural fluid TPS/serum TPS ratio in patients with pleural effusion. We studied prospectively 147 consecutive patients who had pleural effusions: 43 malignant pleural effusions and 104 benign pleural effusions. TPS levels were measured by RIA. The sensitivity and specificity of these measurements were: TPS in pleural fluid (cutoff 20,000 U/L): 0.21 and 0.98; TPS in serum (cutoff 300 U/L); 0.31 and 0.96; pleural fluid TPS/serum TPS ratio (cutoff 1200): 0.07 and 0.99. All these values enhanced the sensitivity of cytologic analysis of pleural fluid. However, we conclude that TPS assay in pleural fluid and serum, and the pleural fluid TPS/serum TPS ratio have limited diagnostic value in patients with pleural effusion.