DRESS Syndrome Scoring System
The RegiSCAR (European Registry of Severe Cutaneous Adverse Reactions) scoring system is the validated diagnostic tool for DRESS syndrome, classifying cases as "no," "possible" (score <2), "probable" (score 2-3), or "definite" (score ≥4) based on clinical and laboratory criteria. 1, 2, 3
RegiSCAR Scoring Criteria
The scoring system evaluates seven key parameters, with points assigned based on presence and severity 1, 4:
Clinical Features (Required for Diagnosis)
- Fever: Temperature >38°C (required criterion) 1, 2
- Skin Rash: Morbilliform (maculopapular) eruption involving >30% body surface area (present in nearly all cases) 1, 4
- Lymphadenopathy: Palpable enlarged lymph nodes in at least two sites 1, 2
Laboratory Abnormalities
Organ Involvement (Critical for Scoring)
- Hepatic: ALT >2 times upper limit of normal 1, 2
- Renal: Creatinine >1.5 times baseline (elevated creatinine is a poor prognostic indicator) 2, 5
- Cardiac: Myocarditis or pericarditis 1, 2
- Pulmonary: Pneumonitis or interstitial infiltrates 2, 6
Temporal Relationship
- Latency Period: Symptom onset 2-6 weeks after drug exposure (distinguishes DRESS from immediate reactions) 1, 2, 3
- Resolution: Prolonged clinical course requiring ≥15 days for improvement after drug withdrawal 1, 4
Score Interpretation
- Score <2: "No case" or "possible" - insufficient criteria met 7, 4
- Score 2-3: "Probable" DRESS - most reported cases fall into this category 7, 4
- Score ≥4: "Definite" DRESS - meets full diagnostic criteria 7, 6, 4
Alternative Diagnostic Criteria
Bocquet's criteria is more efficient for bedside clinical diagnosis, with 77.1% sensitivity compared to RegiSCAR's 60.4% for definite cases, and shows 96.6% concordance with RegiSCAR definite criteria. 5
Bocquet's criteria require three of the following 5:
- Fever
- Skin eruption
- Hematologic abnormalities (eosinophilia, atypical lymphocytes)
- Systemic involvement (lymphadenopathy or organ dysfunction)
Prognostic Indicators Within the Scoring System
Elevated serum creatinine and ferritin levels at presentation predict fatal outcomes, while higher lymphocyte counts indicate need for systemic corticosteroids. 5
- Poor prognosis markers: Elevated creatinine, elevated ferritin, multiorgan involvement 5
- Severity indicators: Higher leukocyte, lymphocyte, and eosinophil counts correlate with prolonged symptom duration 5
- Mortality rate: Approximately 5-9% in reported case series 4
Critical Diagnostic Pitfalls
The vast majority of DRESS cases (77-96%) are classified as "probable/definite" using validated criteria, so a low index of suspicion with incomplete criteria should not delay treatment. 7, 4
- Hypereosinophilia, liver involvement, fever, and lymphadenopathy are significantly associated with probable/definite cases 4
- Skin rash alone is insufficient for diagnosis, as it appears in nearly all cases including "possible" cases that don't meet full criteria 4
- The Japanese DIHS criteria are overly restrictive, capturing only 18.8% of cases that meet RegiSCAR criteria 5
Required Workup for Scoring
- Complete blood count with differential: Assess eosinophilia, atypical lymphocytes, and lymphocyte count 1, 2
- Comprehensive metabolic panel: Evaluate ALT, AST, alkaline phosphatase, bilirubin, BUN, creatinine 1, 2
- Urinalysis: Assess for nephritis 8, 1
- Serum ferritin: Prognostic marker for severe disease 5
- Blood cultures if febrile: Rule out infectious mimics 8, 2
- Skin biopsy if diagnosis uncertain: Shows perivascular lymphocytic infiltration with dermal edema 8, 7