From the Guidelines
An absolute neutrophil count (ANC) of 250 cells/mm³ or greater in ascitic fluid indicates spontaneous bacterial peritonitis (SBP). This diagnostic threshold is critical for initiating prompt treatment of this potentially life-threatening infection in patients with cirrhosis and ascites. When performing a diagnostic paracentesis, the fluid should be sent for cell count with differential, and an elevated neutrophil count above this threshold is diagnostic of SBP even in the absence of positive bacterial cultures, as stated in the guidelines on the management of ascites in cirrhosis 1.
The diagnosis of SBP is based on neutrophil count in ascitic fluid of >250/mm3, which is a well-established threshold, also supported by other studies 1. It's essential to note that approximately 40% of SBP cases have negative cultures despite having an elevated neutrophil count. Once SBP is diagnosed based on this neutrophil threshold, empiric antibiotic therapy should be started immediately, typically with a third-generation cephalosporin such as ceftriaxone or cefotaxime, as recommended in the guidelines 1.
Some key points to consider in the management of SBP include:
- Diagnostic paracentesis should be carried out without delay to rule out SBP in all cirrhotic patients with ascites on hospital admission 1.
- Ascitic fluid culture with bedside inoculation of blood culture bottles should be performed to guide the choice of antibiotic treatment when SBP is suspected 1.
- Immediate empirical antibiotic therapy should be determined with due consideration of the context of SBP, severity of infection, and local bacterial resistance profile 1.
- Patients who have recovered from an episode of SBP should be considered for treatment with norfloxacin, ciprofloxacin, or co-trimoxazole to prevent further episodes of SBP, although the quality of evidence for this recommendation is low 1.
Overall, the threshold of 250 cells/mm³ for ANC in ascitic fluid is a critical diagnostic criterion for SBP, and prompt treatment with empiric antibiotics is essential to improve outcomes in patients with cirrhosis and ascites, as supported by the most recent and highest quality study 1.
From the Research
Diagnosis of Spontaneous Bacterial Peritonitis
To calculate spontaneous bacterial peritonitis (SBP), an absolute neutrophil count (ANC) in the ascitic fluid is used as a diagnostic criterion.
- The diagnostic threshold for SBP is an ANC of ≥ 250 cells/mm3 in the ascitic fluid 2, 3.
- This threshold is used to differentiate SBP from other conditions, such as secondary bacterial peritonitis or culture-negative neutrocytic ascites.
Diagnostic Methods
Several diagnostic methods can be used to diagnose SBP, including:
- Paracentesis: the diagnostic modality of choice, which involves the removal of ascitic fluid for analysis 2, 3.
- Ascitic fluid analysis: includes the measurement of ANC, as well as the use of leukocyte esterase reagent strips for rapid diagnosis 2, 4.
- Blood culture bottles: can be used to improve the culture yield of ascitic fluid 2, 3.
Treatment and Management
The treatment and management of SBP typically involve the use of antibiotics, such as third-generation cephalosporins, as well as supportive care, including albumin infusion 2, 5, 6.