Pseudogout can be difficult to diagnose because it often mimics other medical disorders, including gout. A physician will review the patient’s medical history and typically will perform a physical examination. Additional testing methods are also used to distinguish pseudogout from other painful conditions, such as osteoarthritis. These tests can include:

• Arthrocentesis. A needle is inserted into the affected joint and synovial fluid (fluid that lubricates and protects joints and tendons) is removed for analysis under a microscope. The presence of calcium pyrophosphate dihydrate (CPPD) deposits in the affected joint indicates pseudogout. Pseudogout crystals are positively birefringent (able to split a ray of light in two) under a polarized-light microscope, as compared to gout, where crystals are negatively birefringent. Arthrocentesis is the only testing method that can provide a definitive diagnosis of pseudogout.
  
  
• X-rays. This imaging test may reveal small calcium deposits along joint linings. However, crystal deposits are not detected with x-rays in all cases.
  
  
• Blood tests. Blood testing may show the presence of CPPD deposits in the bloodstream but is often inconclusive. It is most often used along with one or more additional testing methods to rule out other potential causes of joint pain.