What are the CASPAR (Classification Criteria for Psoriatic Arthritis) criteria?

CASPAR Criteria for Psoriatic Arthritis

The CASPAR (ClASsification criteria for Psoriatic ARthritis) criteria are a validated classification system requiring established inflammatory articular disease plus at least 3 points from 7 specific features, with current psoriasis weighted most heavily at 2 points. 1

Prerequisites for Application

Before applying the scoring system, you must first establish the presence of inflammatory articular disease, defined by: 1

• Tender and swollen joints
• Prolonged morning stiffness (typically >30 minutes)
• Immobility-induced stiffness
• Pain involving joints, spine, and/or entheses associated with erythema, warmth, and swelling 1

The 7-Point Scoring System

Once inflammatory disease is confirmed, calculate points from these features (need ≥3 points total): 1

Current psoriasis = 2 points

• Active psoriatic skin or scalp lesions confirmed by examination 1

Personal history of psoriasis = 1 point

• Only counted if current psoriasis is absent 1
• Patient or physician-reported history of psoriasis 1

Family history of psoriasis = 1 point

• Only counted if current psoriasis is absent AND no personal history exists 1
• First- or second-degree relative with psoriasis 1

Typical psoriatic nail dystrophy = 1 point

• Includes onycholysis, pitting, and hyperkeratosis 1

Current dactylitis or history of dactylitis = 1 point

• Swelling of entire digit recorded by a rheumatologist 1

Juxta-articular new bone formation = 1 point

• Seen on plain radiographs of hands or feet 1
• Distinct from osteophytes 2

Rheumatoid factor negativity = 1 point

• By any method except latex; ELISA preferred 1, 3

Performance Characteristics

The CASPAR criteria demonstrate high specificity (98.7%) and good sensitivity (91.4%) for established disease. 1, 3

• In early PsA (<24 months duration), sensitivity drops to 87.4% but specificity remains 99.1% 4
• Superior to Moll and Wright criteria, which have 80.2% sensitivity in early disease 4
• More practical than Vasey and Espinoza criteria (97% sensitivity) due to better specificity 3

Key Clinical Advantages

The CASPAR criteria allow diagnosis even in atypical presentations that older criteria would miss: 5

• Rheumatoid factor-positive patients can still be classified as PsA if they meet the 3-point threshold 5
• Family history alone (without personal skin disease) can contribute to diagnosis, capturing 28.2% of patients who would otherwise be missed 5
• Symmetric polyarticular disease does not exclude PsA diagnosis, unlike Moll and Wright criteria 5

Common Pitfalls to Avoid

Do not apply CASPAR criteria without first confirming inflammatory disease—the criteria are invalid for mechanical, degenerative, or non-inflammatory conditions. 6

Do not count multiple psoriasis features simultaneously—if current psoriasis is present (2 points), you cannot also count personal or family history. 1

Do not rely solely on patient-reported joint swelling—inflammatory arthritis must be objectively confirmed by a clinician detecting warmth, erythema, and swelling. 1, 6

Recommended Diagnostic Workflow

Diagnosis should follow this algorithmic approach: 1

1. Confirm inflammatory musculoskeletal disease through clinical examination showing tender/swollen joints with morning stiffness 1
2. Apply CASPAR scoring to all 7 features systematically 1
3. Obtain rheumatoid factor to exclude RA and potentially gain 1 point if negative 7
4. Order hand/foot radiographs to identify juxta-articular new bone formation 2
5. Measure ESR and CRP as baseline inflammatory markers (not diagnostic but prognostically important) 7

Ideally, psoriasis should be confirmed by a dermatologist and inflammatory musculoskeletal disease by a rheumatologist, though either can be confirmed by an appropriately qualified health professional. 1