HScore is calculated by adding points for nine variables (total 0–337), with higher scores indicating a higher probability of reactive haemophagocytic syndrome.

Variable	Finding	Points
Underlying immunosuppression	None	0
	Present (HIV infection or chronic immunosuppressive therapy)	18
Peak temperature	<38.4°C	0
	38.4–39.4°C	33
	>39.4°C	49
Organomegaly	None	0
	Hepatomegaly or splenomegaly	23
	Hepatomegaly and splenomegaly	38
Number of cytopenias*	1 lineage	0
	2 lineages	24
	3 lineages	34
Peak ferritin	<2000 ng/mL (or µg/L)	0
	2000–6000 ng/mL (or µg/L)	35
	>6000 ng/mL (or µg/L)	50
Triglycerides	<1.5 mmol/L	0
	1.5–4 mmol/L	44
	>4 mmol/L	64
Fibrinogen	>2.5 g/L	0
	≤2.5 g/L	30
AST (SGOT)	<30 U/L	0
	≥30 U/L	19
Bone marrow haemophagocytosis	Absent	0
	Present	35

*Cytopenia is defined as haemoglobin ≤9.2 g/dL (92 g/L), leucocytes ≤5.0 ×10⁹/L and platelets ≤110 ×10⁹/L; the number of cytopenias counts how many of these lineages are cytopenic. Missing data are scored 0 points, as in the original derivation.

HScore for Reactive Haemophagocytic Syndrome