What is Pseudogout
Pseudogout (SOO-doe-gout) is a form of arthritis characterized by sudden, painful swelling in one or more of your joints. These episodes can last for days or weeks. The most commonly affected joint is the knee
Understanding and Diagnosing Pseudogout
To diagnose pseudogout, first of all you have to have the clinical history to suspect pseudogout. So, those symptoms from the history would include acute onset of pain and swelling in a joint, typically a knee or a wrist or an elbow. Typically, there’s a history that they’ve had it before. There may be a history months ago or a year ago that one had a hot, swollen joint, and this has come back months or years later.
Once you’ve suspected the diagnosis of pseudogout, then there are blood tests, and x-rays and special tests that you’ll consider doing. Typically, the blood tests you will do would include a blood test to look for markers of inflammation, so an elevated ESR or CRP. You’ll also want to do a uric acid level, because if the uric acid level is high, it’s much more likely gout than pseudogout.
There are other blood tests that your specialist might want to do, because pseudogout can sometimes be associated with changes in the blood, so it will be important to do some blood test to rule out that as an associated problem. Your specialist will want to do an x-ray of the joint, because it’s not uncommon to see minor calcification along the cartilage of the joint, and that increases the likelihood of the diagnosis of being pseudogout.
The best way to confirm the diagnosis of pseudogout is to put a needle in the joint and remove some fluid. When you remove the fluid, you want to do it for two reasons: One is you want to exclude the fact that you might have an infection, so you’ll send the fluid—the synovial fluid—for a culture, but as importantly, it’s to analyze the fluid for pseudogout crystals.
And under the microscope, with a special manoeuvre to look at it, one can demonstrate the presence of these pseudogout crystals. Sometimes, one’s not able to get a suitable amount of fluid from a joint, and then there are other special tests that one can do to help confirm or deny a diagnosis of gout or pseudogout.
There is one test called the dual energy CT study, which is an x-ray-based CT that can look at joints—the small and large joints—and help decide whether or not the inflammation in a joint is because of pseudogout or gout. This is a test that’s been available for a number of years now, and is a very useful way of helping diagnose pseudogout if you’ve not been able to get any fluid out from the joint.
If you have any questions or concerns about the diagnosis of pseudogout, speak to your healthcare provider or your specialist.
Presenter: Dr. John Wade, Rheumatologist, Vancouver, BC
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