RegiSCAR score = sum of the weighted clinical and laboratory criteria.

Criterion	Definition	Score
Fever	Temperature ≥38.5 °C	Present: 0. Absent or unknown: −1.
Lymphadenopathy	Nodes >1 cm at ≥2 anatomical sites	Present: +1. Absent or unknown: 0.
Eosinophilia when leukocytes are ≥4 × 10⁹/L	Absolute eosinophil count 700–1499/µL or ≥1500/µL	+1 or +2, respectively. <700/µL scores 0.
Eosinophilia when leukocytes are <4 × 10⁹/L	Eosinophils 10–19.9% or ≥20%	+1 or +2, respectively. <10% scores 0.
Atypical lymphocytes	Present on peripheral blood film	Present: +1. Absent or unknown: 0.
Rash extent	Rash affects >50% body surface area	Yes +1; no or unknown 0
Rash morphology	Typical when at least two are present: facial oedema, infiltration, purpura beyond the legs or desquamation	Typical: +1. Not typical: −1. Unknown: 0.
Skin biopsy	Histology compatible with drug hypersensitivity	Compatible or not done: 0. Argues against DRESS: −1.
Internal-organ involvement	Objective involvement attributed to DRESS	None: 0. One organ: +1. At least two organs: +2.
Course	Signs and symptoms persist for ≥15 days	Yes: 0. No or unknown: −1.
Alternative causes excluded	At least three source-specified investigations for alternative causes are performed and negative	Yes: +1. No or insufficient testing: 0.

Use one eosinophilia pathway only; absolute and percentage thresholds are not cumulative.

The possible score range is −4 to +9.

RegiSCAR Score for Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS)