What is the recommended scoring system for diagnosing Systemic Lupus Erythematosus (SLE) using a table with points for clinical and immunological manifestations?

EULAR/ACR 2019 Classification Criteria for SLE Diagnosis

The EULAR/ACR 2019 classification criteria represent the current gold standard scoring system for diagnosing SLE, requiring positive ANA (≥1:80) as an entry criterion, followed by weighted scoring across clinical and immunological domains, with a threshold of ≥10 points indicating SLE classification. 1, 2

Entry Criterion (Mandatory)

• Positive ANA at a titer of ≥1:80 is the absolute entry criterion before applying the weighted criteria 1
• In unselected populations, the 1:160 dilution should be the cut-off point for ANA detection 1
• Without positive ANA, the classification criteria cannot be applied 2

Weighted Scoring System Structure

The 2019 criteria achieve 96.1% sensitivity and 93.4% specificity for SLE classification 2. The system uses weighted points across multiple domains:

Clinical Domains (with point values):

Constitutional:

• Fever (2 points) 2

Hematologic:

• Leukopenia (3 points) 2
• Thrombocytopenia (4 points) 2
• Autoimmune hemolysis (4 points) 2

Neuropsychiatric:

• Delirium (2 points) 2
• Psychosis (3 points) 2
• Seizure (5 points) 2

Mucocutaneous:

• Non-scarring alopecia (2 points) 2
• Oral ulcers (2 points) 2
• Subacute cutaneous OR discoid lupus (4 points) 2
• Acute cutaneous lupus (6 points) 2

Serosal:

• Pleural or pericardial effusion (5 points) 2
• Acute pericarditis (6 points) 2

Musculoskeletal:

• Joint involvement (6 points) 2

Renal:

• Proteinuria >0.5g/24h (4 points) 2
• Renal biopsy Class II or V lupus nephritis (8 points) 2
• Renal biopsy Class III or IV lupus nephritis (10 points) 2

Immunologic Domains (with point values):

Antiphospholipid antibodies:

• Anti-cardiolipin OR Anti-β2GP1 OR Lupus anticoagulant (2 points) 2

Complement proteins:

• Low C3 OR low C4 (3 points) 2
• Low C3 AND low C4 (4 points) 2

SLE-specific antibodies:

• Anti-dsDNA antibody OR Anti-Smith antibody (6 points) 2

Diagnostic Threshold

• Total score ≥10 points = SLE classification 2
• Only the highest weighted criterion within each domain is counted 2
• Criteria must be present at least once and not be better explained by another diagnosis 2

Laboratory Testing Protocol for Diagnosis

Baseline immunological panel should include: 1

• ANA (mandatory entry criterion) 1
• Anti-dsDNA 1
• Anti-Ro/SSA 1
• Anti-La/SSB 1
• Anti-RNP 1
• Anti-Sm 1
• Antiphospholipid antibodies 1
• C3 and C4 complement levels 1

Anti-dsDNA testing strategy: 1

• Use double-screening: last-generation solid phase assay (SPA) first, then Crithidia luciliae immunofluorescence test (CLIFT) for confirmation 1
• If SPA is negative, perform confirmatory CLIFT only when other clinical suspicion signs are present 1

Critical Implementation Points

Secondary care specialists and laboratories should establish standard testing protocols based on the EULAR/ACR 2019 criteria to streamline the diagnostic process 1. The criteria were developed specifically for classification in research settings but are widely applied clinically due to their high sensitivity and specificity 2, 3.

Confirmatory testing of anti-ENA (extractable nuclear antigens) is recommended when ANAs are positive during the diagnostic workup 1. This helps identify specific antibody profiles that contribute to the weighted scoring system 1.

Common Diagnostic Pitfalls

• The 2019 criteria are technically classification criteria designed for research, not formal diagnostic criteria, though they are commonly used diagnostically in practice 3, 4
• Do not apply the scoring system if ANA is negative at ≥1:80 titer—this violates the entry criterion 1, 2
• Clinical judgment remains essential, as some patients with genuine SLE may not meet the 10-point threshold, particularly early in disease course 5, 3
• Laboratory methods for ANA and anti-dsDNA detection vary significantly between institutions, affecting reproducibility 1