Ascitic fluid polymorphonuclear cell count and serum to ascites albumin gradient in the diagnosis of bacterial peritonitis.

The analysis of ascitic fluid has been complicated by several recently reported new tests. To simplify this assessment, we evaluated nine parameters prospectively and simultaneously in blood and ascitic fluid from 285 patients with ascites to determine which were the most reliable for immediate diagnosis of the etiology of the ascites and of its complications. Subjects were first divided into four groups: sterile cirrhotic ascites (n = 201), spontaneous bacterial peritonitis (n = 41), malignant ascites (n = 34), and miscellaneous ascites (n = 9). An ascitic fluid polymorphonuclear count greater than 500/microliters was the test with the greatest accuracy (96%) for the diagnosis of spontaneous bacterial peritonitis. Neither the most precise cutoff values for ascitic fluid pH (less than 7.32) and ascitic fluid lactate (greater than 32 mg/dl), nor their respective blood-ascitic fluid gradients (greater than 0.11 and less than -20 mg/dl) were more reliable indexes of spontaneous bacterial peritonitis, mainly due to the decreased ascitic fluid pH and increased ascitic fluid lactate observed in malignant ascites, tuberculous peritonitis, and pancreatic ascites. A blood-ascitic fluid albumin gradient less than 1.1 g/dl was the most accurate parameter for the diagnosis of malignant ascites (diagnostic efficacy, 93%). Therefore, the etiologic analysis of ascitic fluid might be simplified and the single practice of two tests, ascitic fluid polymorphonuclear cell count and blood-ascitic fluid albumin gradient, provides immediately useful information.