CD64 expression on neutrophils as a potential biomarker for bacterial infection in ascitic fluid of cirrhotic patients

Abstract

Background

CD64 expression on neutrophils surface (CD64N) by flow cytometry has been validated as a rapid biomarker for bacterial infections in both peripheral blood and other biological fluids. Ascites is a common complication in cirrhotic patients that a variety of factors can cause, including bacterial infections. Manual counting of polymorphonuclear (PMN) cells in ascitic fluid and microbiologic culture are essential for its diagnosis. We aimed to validate the determination of CD64N by flow cytometry in ascitic fluid and assess its potential usefulness in the rapid identification of bacterial infections.

Materials and methods

A prospective unicentre study was conducted. Flow cytometry was used to analyse the expression of CD64N in 77 ascitic fluid samples from the initial paracentesis of 60 cirrhotic patients in different admission episodes from November 2021 to December 2022.

Results

Seventeen samples were diagnosed with bacterial infection based on a positive microbiologic culture or by PMN count (>250 PMN/mm³ in ascitic fluid). The median of CD64N MFI was significantly increased in the bacterial infection group (3690.5 MFI [1635.23–6521.18] vs. 1105.9 MFI [737.3–2048.2], p < 0.001). The CD64 MFI ratio of granulocytes to lymphocytes was elevated in the bacterial infection group (13.06 [6.38–24.58] vs. 5.01 [3.38–7.36], p < 0.001). A CD64N ratio higher than 9.9 identified those patients with bacterial infection with 70.6 and 86.7% sensitivity and specificity, with an area under the curve (AUC) of 79.4%.

Conclusion

The CD64N determined by flow cytometry on ascitic fluid could help quickly identify bacterial infections in ascites patients, allowing early antibiotic treatment.

Keywords:

• Bacterial infection
• CD64 expression
• flow cytometry
• ascitic fluid

Author contributions

Study design; David San Segundo, BS, PhD. Sample collection; Aitor Odriozola-Herrán, MD, Ángela Antón-Rodríguez, MD. Data collection; Elena González-López, BS, Mónica Renunico-García, BS, Adriel Roa-Bautista, MD. Data analysis; David San Segundo, BS, PhD, Elena González-López, BS, Mónica Renuncio-García, BS, Adriel Roa-Bautista, MD, Alejandra Comins-Boo, BS, PhD, PhD. Writing of manuscript; David San Segundo, BS, PhD, Elena González-López, BS, Alejandra Comins-Boo, BS, PhD. Clinical perspective; José Igancio Fortea, MD, PhD, Ángela Puente, MD, PhD. Writing review; Marcos López-Hoyos, MD, PhD, Juan Irure-Ventura, BS, José Igancio Fortea, MD, PhD.

Disclosure statement

No potential conflict of interest was reported by the author(s).