Dual-Energy CT: A New Diagnostic Tool for Gout

Allan S. Brett, MD


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In This Article

Abstract and Introduction


Sensitivity and specificity were high in a small computed tomography study.


Gout diagnosis can be elusive: Inexperienced clinicians often are reluctant to perform arthrocentesis, and even experienced clinicians sometimes fail to obtain fluid via arthrocentesis. Dual-energy computed tomography (CT) is a relatively new approach to gout diagnosis that provides images in which gout crystals appear as specifically colored densities in affected joints or periarticular soft tissue (an image can be found at the Journal of Rheumatology).

In a study from Mayo Clinic, 31 patients with suspected gout all underwent both dual-energy CT and successful arthrocentesis. Uric acid crystals were identified in synovial fluid in 12 patients, and CT was positive in all of them (100% sensitivity). In the 19 patients whose fluid was negative for uric acid crystals, CT was negative in 17 (89% specificity). However, the two "false-positive" CT results actually might have been true-positives: In one patient, CT identified gout in the patellar tendon, and an arthrocentesis several months later demonstrated urate crystals; in the second patient, CT identified gout in the wrist, and, despite negative arthrocentesis, the patient responded to gout treatment. Three patients had calcium pyrophosphate crystals in joint fluid, and CT correctly identified all three.


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