How Is Psoriatic Arthritis Diagnosed?

Reviewed by: HU Medical Review Board | Last reviewed: August 2022

Psoriatic arthritis (PsA) is a complex disease to diagnose. There are several reasons why this is the case. First, it shows up differently for each person and can often be mistaken for some other condition. Symptoms can also come and go. And symptoms can evolve and change. This can result in a diagnosis that is delayed or missed altogether.1,2

One big predictor of PsA is psoriasis. This chronic skin condition causes an itchy, scaly rash to appear on the body. Psoriasis often occurs many years before PsA. In fact, about 30 percent of people with psoriasis will go on to develop PsA.1,2

Evaluation by your doctor

A PsA diagnosis begins with a visit to your doctor. Depending on your case, your primary doctor may advise you to see a rheumatologist. This is a doctor who specializes in the diagnosis and treatment of musculoskeletal diseases and autoimmune conditions like PsA and rheumatoid arthritis (RA).3

Most often, a rheumatologist diagnoses PsA. But if you develop psoriasis first, a dermatologist may be the first doctor to recognize your symptoms as PsA.2,3

Medical history and physical exam

Your doctor will talk through your medical history with you and perform a physical exam. The medical history and physical exam are critical tools for assessing whether you have PsA. They can also help rule out other medical conditions.1,2

During the medical history part of your visit, your doctor will ask you:1,2

  • If you have a personal history of psoriasis
  • If you have a family history of psoriasis
  • When your symptoms started

During the physical exam, your doctor will look at your joints to assess:1,2

The joints your doctor will look at include the:1,2

  • Fingers and toes
  • Joints between the bones in the hands
  • Wrist
  • Elbows
  • Shoulders
  • Hips
  • Knees
  • Ankles
  • Joints in the feet
  • Joints around the jaw and sternum

Additional tests to diagnose PsA

After the physical exam, your doctor may order imaging tests to get a clearer picture of the affected joints. These may include:1,2

  • X-ray
  • Ultrasound
  • Magnetic resonance imaging (MRI)
  • Computed tomography (CT) scans

These tests, as well as blood tests, screening tools, and questionnaires, are used to rule out other conditions like RA and gout.1,2

Diagnostic criteria and other tools for PsA

Over the years, researchers have created diagnostic criteria to help with diagnosing PsA. These criteria are:1,2

  • The classification criteria for psoriatic arthritis (CASPAR) – This is a simple, easy-to-use way to assess PsA symptoms. It uses a points system to measure a person’s personal and family history of psoriasis, as well as their physical symptoms. It is the most recent and well established criteria for a PsA diagnosis.
  • Moll and Wright criteria – This is the oldest and most widely known guide to diagnosing psoriatic arthritis.
  • Psoriatic Arthritis Response Criteria (PsARC) – This is a tool created to help evaluate and monitor PsA. During a PsARC exam, a doctor checks 68 different joints on the body for tenderness and 66 joints for swelling.

Know your risk factors

It is important to know whether you are at an increased risk for PsA. If you have psoriasis or a family member has psoriasis, consider getting checked out for PsA. The earlier PsA is diagnosed, the sooner you can begin treatment. And the sooner treatment can begin, the better your overall outcome will be.

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