What Are the Diagnostic Criteria for Psoriatic Arthritis?

Psoriatic arthritis (PsA) is often misdiagnosed or left undiagnosed. This is because its symptoms can vary from person to person, overlap with those of other diseases, and change over time. What makes PsA even more tricky is that there is no single test a doctor can use to confirm a diagnosis. Instead, several tests and exams are used.^1,2

Researchers have worked to create diagnostic criteria to help diagnose people with PsA. The CASPAR and Moll and Wright Criteria are measurements used to help guide PsA diagnosis.^1,2

Classification criteria for psoriatic arthritis (CASPAR)

The classification criteria for psoriatic arthritis (CASPAR) was published in 2006. Since then, it has gained acceptance by both doctors and researchers.^1,2

The CASPAR is simple, easy to use, and specific to PsA symptoms. It uses a points system to confirm a PsA diagnosis.^1,2

Based on the CASPAR, a person has PsA if they have inflammatory arthritis in the joints, spine, or connective tissue between tendons and bone (entheses). They must also have at least 3 symptoms from the following 5 categories:^1,2

• Skin psoriasis
  • Current psoriasis (2 points)
  • Personal history of psoriasis (1 point)
  • Family history of psoriasis (1 point)
• Nail psoriasis. Symptoms may include detachment of the nail from the nail bed, nail pitting, and thickening of the nail (1 point)
• Absence of rheumatoid factor in blood tests (1 point)
• Current or prior history of sausage-like inflammation of the fingers and/or toes (dactylitis) (1 point)

Changes to the bones in the hands and/or feet, as seen in X-rays and other advanced imaging. Changes may include new bone growth or the fusion of bones (1 point).^1,2

Moll and Wright criteria for psoriatic arthritis

Researchers Moll and Wright established the original criteria for PsA in 1973. It is the oldest and most widely known guide to diagnosing psoriatic arthritis.^1,2

To meet the Moll and Wright criteria for PsA, a person with psoriasis who has inflammatory arthritis and a negative blood test for rheumatoid arthritis must also meet one of these 5 subtypes:²

• Distal arthritis – affects mainly the joints in the fingers and toes
• Polyarticular, symmetric arthritis – affects at least 5 or more of the same joints on both sides of the body. For example, both knees, both hips, or the same fingers on both hands are affected.
• Oligoarticular, asymmetric arthritis – affects fewer than five joints, and the joints are not the same on both sides of the body
• Spondylitis predominant – affects mainly the joints between the vertebrae in the spine
• Arthritis mutilans – the most severe form of PsA. This form leads to disfigurement.

Early diagnosis is key

Early diagnosis is so important to prevent or delay the progression of PsA. If left undiagnosed or untreated, the condition can be disabling and disfiguring. A thorough exam using the above criteria is necessary for confirming a PsA diagnosis.^1,2

Know your risk factors. If you have psoriasis, you are more at risk of developing PsA. Talk with your doctor about any signs and symptoms you may have as soon as you start experiencing them.^1,2