Pseudogout Diagnosis

A patient exam and interview along with lab analysis of the joint fluid can confirm or disprove a pseudogout diagnosis. A doctor will want to consider and rule out other possible medical conditions that produce similar symptoms before diagnosing symptoms similar to pseudogout, such as gout and septic arthritis.

Methods of diagnosis may include some or all of the following:

Patient interview

A doctor will ask a patient to describe the onset and pattern of his or her symptoms. They may also ask about family medical history.

Physical exam

A doctor will examine the patient’s affected joint, noting swelling, pain points, and range of motion.

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 fluid from the affected joint—a procedure called joint aspiration—and send it to a lab for analysis.

During analysis, the fluid will be examined under a polarized microscope. A well-trained expert can identify the calcium pyrophosphate (CPP) crystals that cause pseudogout by their shape, color, and reaction to light. If CPP crystals are found in the fluid sample, then CPPD disease is confirmed and pseudogout may be considered as a diagnosis.

See The Joint Aspiration Procedure

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.

See What Is Calcium Pyrophosphate Crystals Deposition (CPPD)?

Blood and urine lab tests

While there are no blood or urine tests to confirm pseudogout, a doctor may order them to help rule out another potential diagnosis, such as gout. A doctor may also order blood and/or urine tests if they suspect a patient’s pseudogout may be due to an underlying medical condition, such as hemochromatosis.

X-rays

The calcium pyrophosphate crystals that cause pseudogout can calcify cartilage. The resulting calcifications, which doctors call chondrocalcinosis, show up on x-rays. X-rays can also show overall joint damage.

It is possible to have chondrocalcinosis or joint damage without having pseudogout, so x-rays should not be the sole diagnostic tool used.

Ultrasound

Chondrocalcinosis that indicates CPPD and possible pseudogout can be seen using ultrasound.

During an ultrasound procedure, chondrocalcinosis can show up as a visible abnormality within the cartilage, suggesting CPPD. In contrast, an abnormality seen along the surface of the cartilage may suggest gout.¹Slobodonick A, Toprover M, Pillinger M. Crystal Arthritis. In: Efthimiou P, ed. Absolute Rheumatology Review. Springer Nature Switzerland AG; 2020; chap 15. Accessed September 15, 2020. https://doi.org/10.1007/978-3-030-23022-7_15 Some experts suggest that these differences are subtle, and it may be difficult to differentiate between gout and pseudogout using traditional ultrasound.²Rosenthal AK, Ryan LM. Calcium Pyrophosphate Deposition Disease. N Engl J Med. 2016;374(26):2575-2584. doi: 10.1056/NEJMra1511117

Computed tomography (CT) scans

Chondrocalcinosis indicative of CPPD and pseudogout can also be seen on a CT scan. This type of imaging scan may be particularly helpful in identifying calcifications in the spine.²Rosenthal AK, Ryan LM. Calcium Pyrophosphate Deposition Disease. N Engl J Med. 2016;374(26):2575-2584. doi: 10.1056/NEJMra1511117

Traditional magnetic resonance imaging (MRI), while useful for visualizing damage to soft tissue, is not especially useful in diagnosing pseudogout or other forms of CPPD disease.²Rosenthal AK, Ryan LM. Calcium Pyrophosphate Deposition Disease. N Engl J Med. 2016;374(26):2575-2584. doi: 10.1056/NEJMra1511117