How should I interpret the results of a diagnostic paracentesis in a patient suspected of having SBP?

Guideline-aligned answer with reasoning, red flags and references. Clinically reviewed by Dr Kola Tytler MBBS CertHE MBA MRCGP.

Posted: 17 August 2025Updated: 17 August 2025 Guideline-Aligned (High Confidence) Clinically Reviewed
Dr Kola Tytler MBBS CertHE MBA MRCGPClinical Lead • iatroX

When interpreting the results of a diagnostic paracentesis for a patient suspected of having spontaneous bacterial peritonitis (SBP), the primary indicator is the ascitic fluid neutrophil (polymorphonuclear leukocyte) count , .

A neutrophil count of 250 cells/mm³ or more is diagnostic of SBP , , . Conversely, a neutrophil count of less than 250 cells/mm³ effectively rules out SBP .

In addition to the cell count and differential, ascitic fluid should also be sent for total protein and culture , . It is important to note that ascitic fluid cultures are only positive in approximately 40% of SBP cases; therefore, a negative culture does not rule out SBP if the neutrophil count is elevated , .

Prompt interpretation of these results is crucial for timely management, as SBP is a common and serious complication in patients with cirrhosis and ascites .

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