Can clear ascitic fluid appearance rule out spontaneous bacterial peritonitis?

The objective of the study was to determine the sensitivity and specificity of abnormal ascitic fluid appearance in the detection of spontaneous bacterial peritonitis (SBP), as a sensitivity approaching 100% could exclude SBP if the fluid is clear. Methods We performed a retrospective review of all ascitic fluid samples sent for cell count over a 4-year period. Spontaneous bacterial peritonitis was defined as an absolute neutrophil count of more than 250 cells/mm3 or a positive culture. Abnormal fluid appearance was defined as hazy, cloudy, or bloody. Results There were 916 ascitic fluid samples analyzed during the study period. Eighteen percent of samples had a clear appearance, whereas 82% were abnormal. Abnormal ascitic fluid appearance had a sensitivity of 98.1% (95% confidence interval, 95.3%-99.5%) and a specificity of 22.7% (95% confidence interval, 19.4%-26.3%) in the detection of SBP. Conclusions Abnormal fluid appearance has a high sensitivity for the detection of SBP. Thus, clear fluid might safely exclude SBP