Table 1.

Grading system for cytokine release syndrome (CRS) associated with CAR T cell toxicity adapted from Lee et al. [13]

CRS parameter	Grade 1	Grade 2	Grade 3	Grade 4
Temperature ≥ 38°C*	Yes	Yes	Yes	Yes
		With
Hypotension (SBP <90 mm Hg)	None	None requiring vasopressors	Requiring a vasopressor with or without vasopressin	Multiple vasopressors (excluding vasopressin)
		And/or†
Hypoxia	None	Requiring low-flow‡ nasal cannula or blow-by oxygen	Requiring HFNC‡, facemask, non-rebreather, or Venturi mask	Requiring positive pressure (e.g., CPAP, BiPAP, intubation and mechanical ventilation)

SBP, systolic blood pressure; HFNC, high-flow nasal cannula; CPAP, continuous positive airway pressure; BiPAP, bilevel positive airway pressure

*Fever must not be attributable to any other cause, and when antipyretic or anticytokine therapy is initiated (e.g., tocilizumab or steroids), CRS grading is driven by hypotension and hypoxia only

†CRS grading is defined by the more severe event, e.g., a febrile patient on a single vasopressor and low-flow nasal cannula would be classified as Grade 3 CRS

‡Low-flow nasal cannula refers to oxygen delivered at ≤ 6 L/min, whereas high flow refers to delivery at >6 L/min