Diagnosing psoriatic arthritis is usually done by process of elimination. Your doctor will give you tests to rule out conditions that cause similar symptoms. These are the most common ones.

Rheumatoid Factor (RF)

  • Blood test done to help rule out rheumatoid arthritis (RA)
  • Looks for a specific antibody seen in the blood of patients with rheumatoid arthritis but missing in those with psoriatic arthritis

Joint Fluid

  • Checks uric acid levels to help rule out gout
  • Fluid is taken from the symptomatic joint with a long needle
  • In patients without gout, the uric acid level is less than 6 mg/dL

Magnetic Resonance Imaging (MRI)

  • To check the joints and soft tissues for inflammation or abnormalities
  • You are asked to lie on your back on a table with your head, torso, and arms strapped down to prevent movement. The table then slides into a tunnel-like space that contains a magnet. You may hear banging or tapping noises from the magnet movement but there is often piped in music to soothe you and mask the noise. Images are taken in body cross sections.
  • The test usually takes 30-60 minutes and is painless.


  • To detect abnormalities of the joints that are only seen in psoriatic arthritis