CD64 Expression on Neutrophils (nCD64) as a Biomarker in Adult Patients With Sepsis: A Cross-Sectional Study

Introduction Neutrophils that are at rest exhibit very low expression of CD64, the high-affinity immunoglobulin fragment crystallizable γ receptor I, which is also found in monocytes. Neutrophils that have been exposed to endotoxins or are infected express more CD64. Objectives The aim of this study was to assess the CD64 biomarker expression on neutrophils using the flow cytometry method and its comparison with total leukocyte count, C-reactive protein (CRP) level, and blood culture sensitivity test in the diagnosis of sepsis in adults. Materials and methods Using the quick Sequential Organ Failure Assessment (qSOFA) scoring criteria, 94 blood samples from individuals with clinical indications of sepsis were included in this investigation. Samples were collected in K2 EDTA (ethylenediaminetetraacetic acid) vacutainers and analyzed for neutrophil CD64 (nCD64) levels using BD FACSLyric^TM flow cytometer (BD, Franklin Lakes, NJ) within 24 hours of collection. Total leukocyte count, CRP levels, and blood culture sensitivity tests were also assessed simultaneously. Results Majority of the patients, i.e., 29 (30.9%), belonged to the age group of 19 to 35 years, with a female preponderance. The mean total leukocyte count was 19.49 ± 8.12 x 10³/µL, mean CRP level was 81.19 ± 56.33 mg/dL, and the mean nCD64 expression - median fluorescence intensity was 197.26 ± 79.56. A positive blood culture was found in 59 (62.8%) cases. Neutrophils showed bright expression of nCD64 in 39 (41.5%) patients, dim expression in 35 (37.2%) patients, and moderate expression in 20 (21.3%) patients in the present study. The correlation between nCD64 expression with CRP, total leukocyte count, and blood culture sensitivity test was statistically significant (p=0.001). nCD64 expression showed a sensitivity of 93.2% and specificity of 91.4% for diagnosing sepsis, with an area under the curve (AUC) of 0.973. This proves nCD64 to be a highly effective biomarker compared to conventional methods. Conclusion nCD64 has a higher sensitivity and specificity as compared to total leukocyte count, CRP levels, and blood culture sensitivity test in the diagnosis of sepsis. It is an effective and rapid test that can enhance sepsis diagnostic accuracy, when combined with other biomarkers. Multicentric research needs to be conducted to validate these findings.