[Spontaneous bacterial peritonitis in liver cirrhosis. What tests to perform on the ascitic fluid?]

Spontaneous bacterial perionitis (SBP) is a relatively frequent complication of liver cirrhosis and is associated with a high mortality if not early recognized and immediately treated. The text-books of Medicine available in Italy suggest the use of traditional laboratory tests (gravity, total protein concentration, Rivalta's test) to whom add white blood cell count for the assessment of the nature transudative (not infected) or exudative (infected) of ascitic fluid; nevertheless, in every day clinical practice, the association between total protein concentration and type of ascitic fluid may be misleading with respect to the diagnosis of SPB. The aim of this retrospective study, undertaken on 86 patients with liver cirrhosis consecutively admitted and separated in two groups, one without and the other with PSB (white blood cell count > 500/mm3), was to identify criteria for diagnosis of PSB. The traditional laboratory tests were significantly different in the two groups but Rivalta's test. Yet, none of them showed a diagnostic measurement sufficient for the use in the diagnosis of PSB (positive predittive value: gravity 41%, Rivalta's test 36%, total protein concentration 40%). The results of this work show the traditional laboratory tests unable to define the nature of the ascitic fluid. For the diagnosis of PSB the only reliable parameter is the white blood cell count.