Tests and diagnosis

By Mayo Clinic Staff

During the exam, your doctor may:

  • Closely examine your joints for signs of swelling or tenderness
  • Check your fingernails for pitting, flaking and other abnormalities
  • Press on the soles of your feet and around your heels to find tender areas

No single test can confirm a diagnosis of psoriatic arthritis. But some types of tests can rule out other causes of joint pain, such as rheumatoid arthritis or gout.

Imaging tests

  • X-rays. Plain X-rays can help pinpoint changes in the joints that occur in psoriatic arthritis but not in other arthritic conditions.
  • Magnetic resonance imaging (MRI). MRI utilizes radio waves and a strong magnetic field to produce very detailed images of both hard and soft tissues in your body. This type of imaging test may be used to check for problems with the tendons and ligaments in your feet and lower back.

Laboratory tests

  • Rheumatoid factor (RF). RF is an antibody that's often present in the blood of people with rheumatoid arthritis, but it's not usually in the blood of people with psoriatic arthritis. For that reason, this test can help your doctor distinguish between the two conditions.
  • Joint fluid test. Using a long needle, your doctor can remove a small sample of fluid from one of your affected joints — often the knee. Uric acid crystals in your joint fluid may indicate that you have gout rather than psoriatic arthritis.
Jan. 29, 2014