Ratios of pleural fluid to serum immunoglobulins in malignant pleural effusions

Pleural fluid and serum protein electrophoresis and quantitative immunoglobulin measurements were carried out in patients with pleural effusions. The mean pleural fluid/serum ratios of IgA, IgG, and IgM were elevated in patients with malignant pleural effusions compared with patients with nonmalignant pleural effusions (P less than 0.04). The sensitivity of a pleural/serum IgA, IgG ratio P greater than 0.6 was 46%, 69%, respectively, and for IgM ratio greater than 0.5 was 28%. The specificity for these same ratios was 89%, 74%, and 100% respectively.