title: Identification of intraarticular and periarticular uric acid crystals with dual-energy CT: initial evaluation.
abstract: OBJECTIVE
  To estimate the accuracy, sensitivity, specificity, and interobserver agreement of dual-energy computed tomography (CT) in detection of uric acid crystals in joints or periarticular structures in patients with arthralgia and patients suspected of having gout, with joint aspiration results as reference standard.
  
  
  METHODS
  With institutional review board approval, patient consent, and HIPAA compliance, 94 patients (age range, 29-89 years) underwent dual-source, dual-energy (80 and 140 kVp) CT of a painful joint. A material decomposition algorithm was used to identify uric acid. Two blinded musculoskeletal radiologists evaluated the dual-energy CT images and classified the examination findings as positive or negative for the presence of uric acid crystals. Reference standard was the result of joint aspiration.
  
  
  RESULTS
  Forty-three of 94 patients (46%) underwent attempted joint aspiration within 1 month of dual-energy CT. Aspiration was successful in 31 of 43 patients (72%). In 12 of 31 patients (39%), uric acid crystals were identified at joint aspiration; in 19 patients, they were not. Readers 1 and 2 had no false-negative findings for uric acid at dual-energy CT. Sensitivity was 100% (12 of 12; 95% confidence interval (CI): 74%, 100%) for both readers. Specificity was 89% (17 of 19; 95% CI: 67%, 99% ) for reader 1 and 79% (15 of 19; 95% CI: 54%, 94%) for reader 2, with near-perfect agreement between the readers (κ = 0.87; range, 0.70-1.00) in the 31 patients who underwent aspiration.
  
  
  CONCLUSIONS
  Initial retrospective assessment suggests that dual-energy CT is a sensitive, noninvasive, and reproducible method for identifying uric acid deposits in joints and periarticular soft tissues in patients suspected of having gout.
authors.affiliation: Department of Radiology, Mayo Clinic, 200 First St SW, Rochester, MN 55905, USA.
authors.forename: Katrina N
authors.initials: KN
authors.lastname: Glazebrook
authors.forename: Luis S
authors.initials: LS
authors.lastname: Guimarães
authors.forename: Naveen S
authors.initials: NS
authors.lastname: Murthy
authors.forename: David F
authors.initials: DF
authors.lastname: Black
authors.forename: Tim
authors.initials: T
authors.lastname: Bongartz
authors.forename: Nisha J
authors.initials: NJ
authors.lastname: Manek
authors.forename: Shuai
authors.initials: S
authors.lastname: Leng
authors.forename: Joel G
authors.initials: JG
authors.lastname: Fletcher
authors.forename: Cynthia H
authors.initials: CH
authors.lastname: McCollough
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D005260:Female; D006073:Gout / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D018709:Statistics, Nonparametric; D013396:Suction; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014527:Uric Acid
chemical_list: D014527:Uric Acid