RESUMEN
BACKGROUND: Cholinesterase is an enzyme mainly synthesized in the liver that might play a role in the differential diagnosis of ascites. We prospectively compared the sensitivity, specificity and diagnostic usefulness of the ascites cholinesterase and the classical parameters, ascites total protein concentration and serum-ascites albumin gradient in the differential diagnosis of ascites. In addition, we evaluated the relationship between those parameters and the degree of liver failure. METHODS: A total of 91 patients with ascites were analyzed. According the final diagnosis, patients were classified in two groups, patients with signs of portal hypertension [n = 78] (60 with chronic liver disease, 5 chronic liver disease and hepatocellular carcinoma, 3 chronic liver disease and spontaneous bacterial peritonitis, 3 chronic liver disease and secondary peritonitis, 7 malignancy with liver involvement) and patients with no signs of portal hypertension [n = 13] (12 patients with peritoneal neoplasia without liver involvement and 1 tuberculous peritonitis). RESULTS: The sensitivity of the test for detecting portal hypertensive ascites was lowest for ascites cholinesterase less than 600 U/L (71.7%); intermediate with ascites total protein concentration less than 25 g/l (87.2%) and highest with serum-ascites albumin gradient at least 11 g/l (93.6%). The specificity for ruling out portal hypertensive ascites was 100 percent for ascites total protein > or = 25 g/l and ascites cholinesterase > or = 600 U/L and, 76.9 percent for serum-ascites albumin gradient < 11 g/l). Diagnostic efficiency (percentage of patients accurately classified) was greater for serum-ascitis albumin gradient (91.2%; IC95: 83-95.8), and lower for ascites total protein content (89%, IC95: 80.3-94.3) and, ascites cholinesterase (75.8%; IC95: 65.5-83.9). Ascites cholinesterase showed a significant relationship (p = 0.007) with the degree of liver failure measured by Pugh's classification. CONCLUSION: Serum-ascites albumin gradient was the test with best performance characteristics to identify patients with ascites related with portal hypertension. Our results suggest that ascites cholinesterase is more associated with the degree of liver failure than with the presence of portal hypertension.