title: Dual energy CT in gout: a prospective validation study.
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 cm(3) to 18.74 cm(3) with a mean of 2.45 cm(3). 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) cm(3) and 0.01 (0.03) cm(3).
  
  
  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.
authors.affiliation: Section of the Rheumatology and the Clinical Epidemiology Unit, Boston University School of Medicine, Boston, MA 02118, USA. hchoius@bu.edu
authors.forename: Hyon K
authors.initials: HK
authors.lastname: Choi
authors.forename: Lindsay C
authors.initials: LC
authors.lastname: Burns
authors.forename: Kamran
authors.initials: K
authors.lastname: Shojania
authors.forename: Nicole
authors.initials: N
authors.lastname: Koenig
authors.forename: Graham
authors.initials: G
authors.lastname: Reid
authors.forename: Mohammed
authors.initials: M
authors.lastname: Abufayyah
authors.forename: Genevieve
authors.initials: G
authors.lastname: Law
authors.forename: Alison S
authors.initials: AS
authors.lastname: Kydd
authors.forename: Hugue
authors.initials: H
authors.lastname: Ouellette
authors.forename: Savvas
authors.initials: S
authors.lastname: Nicolaou
mesh_terms: D005260:Female; D006073:Gout / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014527:Uric Acid / Q000032:analysis
chemical_list: D014527:Uric Acid