DIFFERENTIAL-DIAGNOSIS OF HUMAN ASCITES - INHIBITORS OF THE CONTACT SYSTEM AND TOTAL PROTEINS

To assess their accuracies as markers for malignancy, we assayed alpha2-macroglobulin, Cl-inhibitor, alpha1-protease inhibitor, and total proteins in ascites and plasma from patients with gastrointestinal cancer (n = 15) and non-malignant liver disease (n = 13), using functional and immunologic assays. For all inhibitors and total proteins determined in ascites, the values in the cancer group were significantly higher than the corresponding values in the group with non-malignant liver disease. The diagnostic accuracy for differentiating malignancy-related from non-malignant ascites was 93% for a alpha1-protease inhibitor value greater-than-or-equal-to 50% of the pool plasma value and 90% for alpha2-macroglobulin greater-than-or-equal-to 16%, Cl-inhibitor greater-than-or-equal-to 40% (all functional assays), and total proteins greater-than-or-equal-to 20 g/l (biuret). In conclusion, functional assays for alpha2-macroglobulin, Cl-inhibitor, and alpha1-protease inhibitor and determination of total proteins in ascites appeared to be very informative tests for the differential diagnosis of ascites. The test for alpha1-protease inhibitor gave higher specificity (92% versus 77%) and likelihood ratio for a positive test (12 versus 4) compared with the other tests.