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Extended report
Dual energy CT in gout: a prospective validation study
  1. Hyon K Choi1,2,3,
  2. Lindsay C Burns2,4,
  3. Kamran Shojania2,3,
  4. Nicole Koenig2,
  5. Graham Reid3,
  6. Mohammed Abufayyah3,
  7. Genevieve Law3,
  8. Alison S Kydd3,
  9. Hugue Ouellette5,
  10. Savvas Nicolaou5
  1. Section of Rheumatology and the Clinical Epidemiology Unit, Boston University School of Medicine, Boston, MA, USA
  2. Arthritis Research Centre of Canada, Vancouver, Canada
  3. Rheumatology Division, University of British Columbia, Vancouver, Canada
  4. Department of Dermatology and Skin Science, University of British Columbia, Vancouver, Canada
  5. Radiology Department, Department of Medicine, Vancouver General Hospital, University of British Columbia, Vancouver, Canada
  1. Correspondence to Hyon K. Choi, Professor of Medicine, Section of the Rheumatology and the Clinical Epidemiology Unit, Boston University School of Medicine, Boston, MA 02118, USA; hchoius{at}bu.edu

Abstract

Objective The authors prospectively determined: (1) the specificity and sensitivity of dual energy CT (DECT) for gout; and (2) the interobserver and intraobserver reproducibility for DECT urate volume measurements.

Methods Forty crystal-proven gout patients (17 tophaceous) and 40 controls with other arthritic conditions prospectively underwent DECT scans of all peripheral joints using a gout protocol that color-codes the composition of tissues. A blinded radiologist identified urate deposition to calculate specificity and sensitivity of DECT for gout. Inter-rater volumetric reproducibility was determined by two independent radiologists on 40 index tophi from the 17 tophaceous gout patients using automated software.

Results The mean age of the 40 gout patients was 62 years, the mean gout duration was 13 years and 87% had a history of urate-lowering therapy (ULT). The specificity and sensitivity of DECT for gout were 0.93 (95% CI, 0.80 to 0.98) and 0.78 (0.62 to 0.89), respectively. When the authors excluded three gout cases with unreadable or incomplete scans, the sensitivity was 0.84 (95% CI, 0.68 to 0.94). The urate volumes of 40 index tophi ranged from 0.06 cm3 to 18.74 cm3 with a mean of 2.45 cm3. Interobserver and intraobserver intraclass correlation coefficients for DECT volume measurements were 1.00 (95% CI, 1.00 to 1.00) and 1.00 (95% CI, 1.00 to 1.00) with corresponding bias estimates (SD) of 0.01 (0.00) cm3 and 0.01 (0.03) cm3.

Conclusions These prospective data indicate high reproducibility of DECT urate volume measures. The specificity was high, but sensitivity was more moderate, potentially due to frequent ULT use in our patients.

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Footnotes

  • Funding This study was supported by investigator initiated research grants from Takeda Pharmaceuticals. The sponsor had no role in the design and conduct of the study; collection, management, analysis and interpretation of the data; and preparation, review or approval of the manuscript.

  • Competing interests Dr Choi has served on advisory boards for Takeda Pharmaceuticals, URL Pharma and Savient Pharmaceuticals.

  • Patient Consent Obtained.

  • Ethics approval Approval provided by the University of British Columbia Behavioural Research Ethics Board.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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