What Are the CASPAR Criteria for Psoriatic Arthritis?

The Classification Criteria for Psoriatic Arthritis (CASPAR) were developed in 2006 to improve the accuracy of diagnosing psoriatic arthritis (PsA).

The CASPAR criteria are based on a combination of clinical features and laboratory findings.

The CASPAR criteria for PsA are as follows:

1. Presence of inflammatory arthritis: This is the most important criterion, and it requires that a person have at least one swollen or tender joint.

2. Evidence of psoriasis: This can include any of the following:

- A history of psoriasis

- Current psoriasis

- Psoriatic nail changes

- A family history of psoriasis

3. Absence of rheumatoid factor: This is a blood test that is often positive in people with rheumatoid arthritis, but it is usually negative in people with PsA.

4. Absence of anti-cyclic citrullinated peptide (anti-CCP) antibodies: This is another blood test that is often positive in people with rheumatoid arthritis, but it is usually negative in people with PsA.

5. Sacroiliitis: This is inflammation of the sacroiliac joints, which are located at the base of the spine. Sacroiliitis can be seen on X-rays or magnetic resonance imaging (MRI).

6. Dactylitis: This is inflammation of an entire finger or toe. Dactylitis can be seen on X-rays or MRI.

7. Enthesitis: This is inflammation of the entheses, which are the areas where tendons and ligaments attach to bone. Enthesitis can be seen on X-rays or MRI.

8. Minimal radiographic changes of PsA: These changes can be seen on X-rays or MRI, and they include:

- Joint erosions

- Joint space narrowing

- Osteophyte formation

- Ankylosis (fusion of the joints)

To meet the CASPAR criteria for PsA, a person must have at least 3 of the following criteria:

- Inflammatory arthritis

- Evidence of psoriasis

- Absence of rheumatoid factor

- Absence of anti-CCP antibodies

- Sacroiliitis

- Dactylitis

- Enthesitis

- Minimal radiographic changes of PsA

The CASPAR criteria are not perfect, and they may not be able to diagnose all cases of PsA. However, they are a useful tool for diagnosing PsA and for differentiating it from other types of arthritis.