What is the indication for ascitic fluid neutrophil count in the workup of spontaneous bacterial peritonitis (SBP)?

Updated: Nov 26, 2018
  • Author: Thomas E Green, DO, MPH, MMM, CPE, FACEP, FACOEP; Chief Editor: Jeter (Jay) Pritchard Taylor, III, MD  more...
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Answer

An ascitic fluid neutrophil count of more than 500 cells/µL is the single best predictor of spontaneous bacterial peritonitis, with a sensitivity of 86% and specificity of 98%. Lowering the ascitic fluid neutrophil count to more than 250 cells/µL results in an increased sensitivity of 93% but a lower specificity of 94%. (For simplicity, a threshold of 250 cells/µL is used for the remainder of this discussion.)

An exciting new development in the rapid diagnosis of spontaneous bacterial peritonitis is the proposed use of reagent strips that detect leukocyte esterase, which can be read at the bedside using a portable spectrophotometric device. In a pilot study that compared the reagent strips with the manual laboratory polymorphonuclear leukocyte count, the strips achieved a 100% sensitivity in diagnosis of spontaneous bacterial peritonitis. [16]

This diagnostic method holds promise in replacing manual cell counting, which is time-consuming and is often unavailable in many laboratories "after hours". Use of these reagent strips may result in a significant reduction of the time from paracentesis to presumptive diagnosis and antibiotic treatment of spontaneous bacterial peritonitis.

In a small cohort, the average time saved from dipstick to laboratory results ranged from 2.73 hours (dipstick to validated result from automated counter) to 3 hours (dipstick to validated manual cell count of ascitic fluid). Although promising, this diagnostic method has not been investigated in a large-scale study.


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