Q&A column

Editor: Frederick L. Kiechle, MD, PhD

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Q. Ordering clinicians are requesting that our laboratory flag abnormally high absolute neutrophil counts (ANC) on peritoneal fluids. We cannot find sources for reference ranges, but there is literature that states that a polymorphonuclear cell count greater than 250/μL is a reliable discriminatory test for bacterial peritonitis. We would like to use this as our reference and flag results with an ANC greater than 250 cells/μL as abnormally high. Is this acceptable?

A.April 2024—Numerous guidelines agree that the diagnosis of spontaneous bacterial peritonitis should be based on an ANC greater than 250 cells/μL in peritoneal fluid from a patient with ascites. This ANC result is sufficient cause for initiating empirical antibiotic therapy. This is because patients with spontaneous bacterial peritonitis usually do not display the typical signs and symptoms of infection, such as fever, abdominal pain, and an elevated white blood cell count on a CBC. It is more likely that these patients will present with encephalopathy, decreasing renal function, or gastrointestinal bleeding or will be asymptomatic.

It is important that the laboratory notify the clinical care teams of an ANC result greater than 250 cells/μL found while performing a diagnostic paracentesis to diagnose spontaneous bacterial peritonitis. At a minimum, the findings should be flagged as abnormally high in the lab report. This will give patient care teams the best chance of starting antibiotic therapy before the patient becomes septic or goes into septic shock.

Aithal GP, Palaniyappan N, China L, et al. Guidelines on the management of ascites in cirrhosis. Gut. 2021;70(1):9–29.

Biggins SW, Angeli P, Garcia-Tsao G, et al. Diagnosis, evaluation, and management of ascites, spontaneous bacterial peritonitis and hepatorenal syndrome: 2021 practice guidance by the American Association for the Study of Liver Diseases. Hepatology. 2021;74(2):1014–1048.

European Association for the Study of the Liver. EASL clinical practice guidelines on the management of ascites, spontaneous bacterial peritonitis, and hepatorenal syndrome in cirrhosis. J Hepatol. 2010;53(3):397–417.

Wong CL, Holroyd-Leduc J, Thorpe KE, Straus SE. Does this patient have bacterial peritonitis or portal hypertension? How do I perform a paracentesis and analyze the results? JAMA. 2008;299(10):1166–1178.

Timothy Skelton, MD, PhD
Medical Director, Core Laboratory and Clinical Informatics
Lahey Hospital and Medical Center
Medical Director
Laboratory and Pathology Informatics
Beth Israel Lahey Health
Former Member, CAP Hematology/Clinical Microscopy Committee