Neutrophil CD64, Monocyte HLA-DR, and Immune Dysregulation Index as Biomarkers for Severe Coronavirus Disease of 2019 Infection, Bacterial Sepsis, and Other Systemic Inflammatory States.

PURPOSE: Differentiating bacterial sepsis (BS), severe coronavirus disease of 2019 (SCOV-19), and noninfectious systemic inflammatory response syndrome (SIRS) remains challenging due to overlapping clinical features. We evaluated the diagnostic and prognostic utility of neutrophil CD64 (nCD64), Monocyte human leukocyte antigen-DR (mHLA-DR), and the immune dysregulation index (IDI) across these conditions.

MATERIALS AND

METHODS

In this prospective observational study, 150 intensive care unit (ICU) patients were enrolled: BS (n = 44), SCOV-19 (n = 46), SIRS (n = 30), and healthy controls (n = 30). Flow cytometric quantification of nCD64 and mHLA-DR was performed, and IDI was calculated as (nCD64/mHLA-DR) ×100. Clinical, laboratory, and outcome data were analyzed to assess group differences and diagnostic performance.

RESULTS

nCD64 expression was significantly elevated in sepsis (median 2310 antibody bound per cell) compared with SCOV-19 (931), SIRS (1034), and controls (348; P = 0.001). mHLA-DR was suppressed in sepsis and SCOV-19 (2711 and 2522) relative to SIRS (10,113) and controls (14,950; P = 0.031). IDI was highest in sepsis (84.16), intermediate in SCOV-19 (38.4), lower in SIRS (9.8), and minimal in controls (2.1; P < 0.0001). IDI demonstrated excellent discrimination between disease and controls (area under the curve [AUC] = 1.0), sepsis and SIRS (AUC = 0.96), and moderate discrimination between sepsis and SCOV-19 (AUC = 0.75). Higher IDI values were associated with mortality in both sepsis (107.80 vs. 35.00; P = 0.032) and SCOV-19 (73.02 vs. 19.80; P < 0.0001).

CONCLUSION

Immune phenotyping using nCD64, mHLA-DR, and IDI effectively differentiates infectious from sterile inflammation and predicts mortality, supporting its integration into ICU risk stratification.