Dual-energy CT for the diagnosis of gout: an accuracy and diagnostic yield study

Tim Bongartz, Katrina N Glazebrook, Steven J Kavros, Naveen S Murthy, Stephen P Merry, Walter B Franz 3rd, Clement J Michet, Barath M Akkara Veetil, John M Davis 3rd, Thomas G Mason 2nd, Kenneth J Warrington, Steven R Ytterberg, Eric L Matteson, Cynthia S Crowson, Shuai Leng, Cynthia H McCollough, Tim Bongartz, Katrina N Glazebrook, Steven J Kavros, Naveen S Murthy, Stephen P Merry, Walter B Franz 3rd, Clement J Michet, Barath M Akkara Veetil, John M Davis 3rd, Thomas G Mason 2nd, Kenneth J Warrington, Steven R Ytterberg, Eric L Matteson, Cynthia S Crowson, Shuai Leng, Cynthia H McCollough

Abstract

Objectives: To assess the accuracy of dual-energy CT (DECT) for diagnosing gout, and to explore whether it can have any impact on clinical decision making beyond the established diagnostic approach using polarising microscopy of synovial fluid (diagnostic yield).

Methods: Diagnostic single-centre study of 40 patients with active gout, and 41 individuals with other types of joint disease. Sensitivity and specificity of DECT for diagnosing gout was calculated against a combined reference standard (polarising and electron microscopy of synovial fluid). To explore the diagnostic yield of DECT scanning, a third cohort was assembled consisting of patients with inflammatory arthritis and risk factors for gout who had negative synovial fluid polarising microscopy results. Among these patients, the proportion of subjects with DECT findings indicating a diagnosis of gout was assessed.

Results: The sensitivity and specificity of DECT for diagnosing gout was 0.90 (95% CI 0.76 to 0.97) and 0.83 (95% CI 0.68 to 0.93), respectively. All false negative patients were observed among patients with acute, recent-onset gout. All false positive patients had advanced knee osteoarthritis. DECT in the diagnostic yield cohort revealed evidence of uric acid deposition in 14 out of 30 patients (46.7%).

Conclusions: DECT provides good diagnostic accuracy for detection of monosodium urate (MSU) deposits in patients with gout. However, sensitivity is lower in patients with recent-onset disease. DECT has a significant impact on clinical decision making when gout is suspected, but polarising microscopy of synovial fluid fails to demonstrate the presence of MSU crystals.

Keywords: Dual energy CT scanning; Gout; accuracy.

Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Figures

Figure 1
Figure 1
Patient flow, diagnostic accuracy study. DECT, dual-energy computer tomography; MSU, monosodium urate.
Figure 2
Figure 2
Dual-energy CT images. Arrows indicate MSU deposition (MSU deposits colour coded in green). (A) Subject accuracy study with acute gouty arthritis of the wrist (three-dimensional (3D) reconstruction image); (B) Subject accuracy study with advanced osteoarthritis of the knee, synovial fluid analysis negative for MSU crystals; (C) Subject diagnostic yield study with elbow pain and swelling, synovial fluid analysis negative for MSU crystals; (D) Subject diagnostic yield study with knee pain and swelling, synovial fluid analysis negative for MSU crystals. MSU, monosodium urate.
Figure 3
Figure 3
Patient flow, diagnostic yield study. DECT, dual-energy computer tomography; US, ultrasound.

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