A doctor will want to rule out other possible conditions that can cause symptoms similar to pseudogout, such as gout and septic arthritis. A patient exam and interview along with a lab analysis of the joint fluid can confirm or disprove a pseudogout diagnosis.
Methods of diagnosis may include some or all of the following:
Physical exam. A doctor will examine the patient's affected joint, noting swelling, pain points, and range of motion.
Patient interview. A doctor will ask a patient about family history and to describe the onset and pattern of his or her symptoms.
Joint fluid analysis. The most dependable way to diagnose pseudogout is through joint fluid analysis. A doctor will use a needle to extract a small amount of synovial joint fluid from the affected joint and send it to a lab to be examined under a polarized microscope. A well-trained expert can identify calcium pyrophosphate crystals by factors such as shape, color and how they react to light. If calcium pyrophosphate crystals are found in the fluid sample, then CPPD is confirmed and pseudogout is the likely cause of symptoms.
Read more: What Is a Synovial Joint?
X-rays. When calcium pyrophosphate crystals have calcified the cartilage, known as chondrocalcinosis, it will show up on an X-ray. An X-ray can also show overall joint damage. However, it is possible to have chondrocalcinosis or joint damage without having pseudogout, so X-rays should not be the sole diagnostic tool used.
Ultrasonography. Early research suggests ultrasonography (ultrasound) may be better than X-rays at detecting calcification on some joints, but not on deeper-tissue joints such as the spine. More research studies need to be done regarding ultrasound's efficacy in detecting the presence of calcium pyrophosphate crystals in joints.
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Synovial biopsy. Though infrequently done, it is possible to detect pseudogout with a synovial biopsy. During a biopsy a doctor will arthroscopically remove a part of the membrane that encapsulates the affected joint, called the synovial membrane. The synovial membrane can be tested and examined for calcium pyrophosphate crystals.
Blood & urine lab tests. Because calcium pyrophosphate crystals seem to originate and stay in the joint tissue, there are no blood or urine tests to confirm pseudogout. A doctor might order these tests, however, to determine if symptoms are due to gout rather than pseudogout.
It is important to note that a joint can contain calcium pyrophosphate crystals as well as other crystals, including gout-causing urate crystals. Likewise, calcium pyrophosphate crystals can be found along with evidence of infection (septic arthritis). One diagnosis does not necessarily rule out the other.