Table 3.

Myeloid phenotypes diagnostic criteria in severe COVID-19 and targeted investigation and therapy

	Hyper-activated monocytes/macrophage (HAMM)	Transient immune-depression (TID)	Persistent immune-depression (PID)
Dynamic diagnostic criteria
M-MDSC day 0a,b	< 5%
mHLA-DR day 0a	> 30,000 AB/C	< 30,000 AB/C
mHLA-DR day 5–7a		> 15,000 AB/C	< 15,000 AB/C
Targeted investigation	Screen for MAS-like: myelogram		Track VAP
Targeted therapy	If MAS-like, consider immunotherapy (e.g. Anti-IL6)		Consider empiric antibiotics by day 5–7

M-MDSC, monocytes myeloid-derived suppressor cell to total monocytes ratio defined as CD19⁻ CD14⁺ CD15⁻CD11b⁺HLA-DR⁻ cells/CD19⁻ CD14⁺ CD15⁻ cells; mHLA-DR, monocytes Human leukocyte antigen-DR; AB/C, antibody per cell; MAS, macrophage activation syndrome; VAP, ventilator-associated pneumonia

^aFollowing ICU admission

^bM-MDSC > 18% is associated with 28-day mortality in PID and TID, with PID systematically associated with secondary infection