Entry Prerequisite - Must Be Present
The CASPAR criteria apply only to patients with established inflammatory articular disease - this includes peripheral arthritis, axial disease, or enthesitis. If inflammatory articular disease is not present or not yet confirmed, CASPAR does not apply. This tool scores the 5 CASPAR domains for eligible patients.
📋 What the CASPAR Criteria Do
The CASPAR (ClASsification criteria for Psoriatic ARthritis) criteria classify inflammatory articular disease as psoriatic arthritis based on five clinical and laboratory domains. The key insight is that psoriasis - particularly current psoriasis scored 2 points - is the single strongest classifier, reflecting its high specificity for PsA when combined with inflammatory joint disease.
These criteria were validated in the original CASPAR study group cohort of 588 PsA patients and 536 controls (other inflammatory arthritis), achieving sensitivity 91.4% and specificity 98.7% - remarkably high specificity that reflects how distinctive the combination of psoriasis and inflammatory articular disease is.
📊 Interpreting the Score
| Score | Classification | Notes |
|---|
| < 3 | Does Not Meet CASPAR | Insufficient evidence for PsA classification. Consider alternative diagnoses. |
| 3 or more | Meets CASPAR Criteria | Classifies as psoriatic arthritis when inflammatory articular disease is confirmed as prerequisite. |
Maximum possible CASPAR score is 6 (current psoriasis = 2, plus one point each for nail dystrophy, negative RF, dactylitis, and radiographic changes). A patient with current psoriasis alone already contributes 2 of the 3 required points - a single additional feature suffices for classification.
💡 Pearls and Pitfalls
✓
Current psoriasis alone (2 pts) nearly meets criteria. Any patient with active psoriasis and inflammatory arthritis needs only one more domain (nail disease, negative RF, dactylitis, or juxta-articular new bone) to meet CASPAR. In clinical practice, approximately 85% of PsA patients have current or past psoriasis, making this the dominant domain.
✓
RF negativity scores a point, not RF positivity. Approximately 7-10% of PsA patients have positive RF, which is important because positive RF reduces the CASPAR score. A seropositive patient with psoriasis and arthritis needs two additional domains to meet criteria rather than one. This reflects the distinctly seronegative nature of most PsA.
✓
Family history of psoriasis applies when there is no personal history. The psoriasis domain allows scoring 1 point for a first- or second-degree relative with psoriasis, but only if the patient does not have personal or current psoriasis. In clinical practice, family history alone rarely drives classification unless combined with dactylitis and negative RF.
⚠
CASPAR are classification criteria, not diagnostic criteria. A score of 3 or more classifies PsA for research documentation. Clinical diagnosis also requires excluding mimics such as reactive arthritis, RA with incidental psoriasis, and axial spondyloarthritis in a patient with psoriasis. The CASPAR criteria should not be used in isolation to make a treatment decision.
⚠
Juxta-articular new bone differs from osteophytes. Radiographic periosteal new bone in PsA is ill-defined and located adjacent to joint margins - not the sharp, well-defined osteophytes of osteoarthritis. Distinguishing these requires careful radiograph review. This domain is less commonly scored in clinical practice.
🔬 Evidence
CASPAR was developed by Taylor, Gladman, Helliwell, and colleagues through the CASPAR study group, an international collaboration, and published in Arthritis and Rheumatism in 2006. The criteria were derived from a case-control study of 588 PsA patients and 536 controls with other inflammatory arthritis from 30 international rheumatology centers. The specificity of 98.7% is among the highest of any rheumatologic classification criteria, reflecting the distinctive clinical phenotype of PsA.
View References▾
1
Taylor W, Gladman D, Helliwell P, et al. (CASPAR Study Group). Classification criteria for psoriatic arthritis: development of new criteria from a large international study. Arthritis Rheum. 2006;54(8):2665-2673. Original criteria development in 588 PsA patients.
2
Coates LC, Conaghan PG, Emery P, et al. Sensitivity and specificity of the classification of psoriatic arthritis criteria in early psoriatic arthritis. Arthritis Rheum. 2012;64(10):3150-3155. Validation in early PsA demonstrates sensitivity 87.8% in early disease.
3
Gladman DD, Helliwell P, Mease PJ, et al. Assessment of patients with psoriatic arthritis. J Rheumatol. 2004;31(7):1267-1269. Framework for PsA assessment using CASPAR.