Session Type: Abstract Submissions (ACR)
Background/Purpose: To evaluate the diagnostic accuracy of Dual-Energy Computed Tomography (DECT) and ultrasound for detecting monosodium urate crystal deposits in patients with clinically suspected gout.
Methods: In this case control study DECT and comprehensive ultrasound of feet, knees, hands, wrists, and elbows were performed bilaterally in 60 consecutive patients (49 males; 11 females; mean age, 62 years; age range, 36-82 years) of a tertiary rheumatology referral center with suspected gout and compared with pooled clinical information including polarization microscopy, maximum documented uric acid levels, presence of podagra and the final rheumatological diagnosis as standard-of-reference.
Results: Finally, 39 patients were classified as gout positive, 31 of which had been newly diagnosed. Sixteen of these patients had gout and a concomitant rheumatic disease. Although an experienced rheumatologist aimed at receiving material from tissue or joint aspirates of every patient, if necessary with ultrasound guidance, the diagnosis could be confirmed by polarization microscopy only in 46% of the gout patients.
DECT had a sensitivity of 84.6%. Ultrasound had a sensitivity of 100%. The specificity for the diagnosis of gout was 85.7% for DECT and 76.2% for ultrasound. The positive predictive value was 0.92 for DECT and 0.89 for ultrasound. The negative predictive value was 0.75 for DECT and 1 for ultrasound.
Uric acid deposits occurred most commonly in the medial and lateral aspects of the knee joint, in the quadriceps tendon and in the first MTP 1 joints. The evaluation on a joint-basis compared to ultrasound as reference revealed a sensitivity of 46.2% and a specificity of 97.6% for DECT. Ultrasound detected smaller crystal deposits than DECT. DECT failed to show crystal deposits on the cartilage, representing the “ultrasound double contour sign”, but delineated larger intra-articular and extra-articular tophi.
Ultrasound was false positive in one patient with calcium pyrophosphate dihydrate disease (CPPD), hydroxyapatite deposition disease and rheumatoid arthritis, respectively, and in two patients with severe peripheral arterial occlusive disease.
DECT was false positive in 3 patients showing minimal deposits suggestive of gout tophi in the lateral menisci. One patient was finally diagnosed with CPPD, one with psoriatic arthritis and one with undifferentiated oligoarthritis. Small signals that are not representing urate deposits also appear in nails.
The DECT volumetry computed a mean uric acid deposit load of 2.0 cm3 (SD 9.6 cm3). A mean effective dose between 0.4 and 0.5 mSv was estimated.
Conclusion: DECT is specific for the diagnosis of gout particularly when excluding small signals in the lateral menisci and in the nails. However, it fails to detect small uric acid deposits. It is particularly useful for patients with ambivalent findings, concomitant rheumatic diseases, and for those whose joint aspiration and microscopy did not successfully detect gout crystals.
W. A. Schmidt,
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/systematic-staging-for-uric-acid-deposits-with-dual-energy-computed-tomography-and-ultrasound-in-suspected-gout/