Medical diagnosis is an inexact science. You might know this already from personal experience, and if you do you have a lot of company. A lot of frustrated, exasperated company—because there’s nothing more discouraging than receiving a diagnosis that turns out to be inaccurate.
That’s one reason we were interested in a recent report from the Mayo Clinic about improvements in the process for diagnosing gout. The research, led by Tim Bongartz, M.D., a Mayo Clinic rheumatologist, indicates that dual-energy CT scans (DECT) can be helpful for identifying cases of gout that have been undiagnosed or misdiagnosed as other conditions.
Typically, physicians test for gout by drawing fluid or tissue from an affected area and examining the sample for the presence of uric acid crystals. The test, known as a needle aspirate, is reliable—especially at the onset of gout symptoms—but it’s not perfect.
If the needle aspirate fails to reveal the presence of uric acid crystals, patients might be diagnosed with—and treated for—other conditions, such as rheumatoid arthritis or chronic tendinitis in the elbow or Achilles tendon. And it probably won’t surprise you to hear that those treatments will not be effective. Medication and treatment for, say, rheumatoid arthritis is quite different from medication and treatment for gout. It won’t provide relief and it certainly won’t solve the problem. Thus, patients continue to live with pain, and in many cases the condition progresses.
“The first flare of gout most commonly occurs in the big toe, but gout can affect pretty much every joint in the body, and the more gout flares you have the higher likelihood that other joint areas will be affected,” Dr. Bongartz explains. That includes the feet, ankles, knees, fingers, wrists, and elbows.
So, even if the first diagnostic test turns up negative for gout, if the pain persists and the treatment isn’t providing relief it might be worthwhile for your doctor to take a second look. That’s where DECT scan comes in, literally allowing physicians to look for uric acid crystals and to visualize where gout might occur.
In the recent Mayo Clinic study, the DECT scan detected the presence of uric acid crystals in 30 percent of patients who had initially tested negative for gout. The scan was then followed by a more precisely targeted needle aspirate that confirmed the presence of the uric acid crystals.
The DECT scan is not intended to replace the needle aspirate, which is the preferred method for diagnosis. DECT scans are good for detecting the presence of uric acid crystals around ligaments and tendons and they can be helpful for examinations when a needle can’t or shouldn’t be used (when the area is infected, for instance). Yet DECT scans have limitations as well: They’re not especially good for detecting gout in early stages or detecting small or less dense crystals. They simply offer a way to double-check the results of a negative gout diagnosis, should the need arise.
The paper on the Mayo Clinic study led by Dr. Bongartz, “Dual-energy CT for the diagnosis of gout: an accuracy and diagnostic yield study,” was published in the March 25, 2014, edition of Annals of the Rheumatic Diseases. Other studies on the use of DECT scans for gout diagnosis have been conducted in Canada, Germany, and New Zealand. Researchers are encouraged by the findings, and if the use of DECT scans leads to more accurate diagnosis of gout we’re encouraged, too.