title: Study for Updated Gout Classification Criteria: Identification of Features to Classify Gout.
abstract: OBJECTIVE
  To determine which clinical, laboratory, and imaging features most accurately distinguished gout from non-gout.
  
  
  METHODS
  We performed a cross-sectional study of consecutive rheumatology clinic patients with ≥1 swollen joint or subcutaneous tophus. Gout was defined by synovial fluid or tophus aspirate microscopy by certified examiners in all patients. The sample was randomly divided into a model development (two-thirds) and test sample (one-third). Univariate and multivariate association between clinical features and monosodium urate-defined gout was determined using logistic regression modeling. Shrinkage of regression weights was performed to prevent overfitting of the final model. Latent class analysis was conducted to identify patterns of joint involvement.
  
  
  RESULTS
  In total, 983 patients were included. Gout was present in 509 (52%). In the development sample (n = 653), the following features were selected for the final model: joint erythema (multivariate odds ratio [OR] 2.13), difficulty walking (multivariate OR 7.34), time to maximal pain <24 hours (multivariate OR 1.32), resolution by 2 weeks (multivariate OR 3.58), tophus (multivariate OR 7.29), first metatarsophalangeal (MTP1) joint ever involved (multivariate OR 2.30), location of currently tender joints in other foot/ankle (multivariate OR 2.28) or MTP1 joint (multivariate OR 2.82), serum urate level >6 mg/dl (0.36 mmoles/liter; multivariate OR 3.35), ultrasound double contour sign (multivariate OR 7.23), and radiograph erosion or cyst (multivariate OR 2.49). The final model performed adequately in the test set, with no evidence of misfit, high discrimination, and predictive ability. MTP1 joint involvement was the most common joint pattern (39.4%) in gout cases.
  
  
  CONCLUSIONS
  Ten key discriminating features have been identified for further evaluation for new gout classification criteria. Ultrasound findings and degree of uricemia add discriminating value, and will significantly contribute to more accurate classification criteria.
authors.affiliation: University of Otago, Wellington, New Zealand.
authors.forename: William J
authors.initials: WJ
authors.lastname: Taylor
authors.affiliation: Radboud University Medical Centre, Nijmegen, The Netherlands.
authors.forename: Jaap
authors.initials: J
authors.lastname: Fransen
authors.affiliation: Radboud University Medical Centre, Nijmegen, The Netherlands.
authors.forename: Tim L
authors.initials: TL
authors.lastname: Jansen
authors.affiliation: University of Auckland, Auckland, New Zealand.
authors.forename: Nicola
authors.initials: N
authors.lastname: Dalbeth
authors.affiliation: University of Pennsylvania and VA Medical Center, Philadelphia.
authors.forename: H Ralph
authors.initials: HR
authors.lastname: Schumacher
authors.affiliation: University of Otago, Wellington, New Zealand.
authors.forename: Melanie
authors.initials: M
authors.lastname: Brown
authors.affiliation: Chiang Mai University, Chiang Mai, Thailand.
authors.forename: Worawit
authors.initials: W
authors.lastname: Louthrenoo
authors.affiliation: Hospital General de México, Mexico City, Mexico.
authors.forename: Janitzia
authors.initials: J
authors.lastname: Vazquez-Mellado
authors.affiliation: Nasonova Research Institute of Rheumatology, Moscow, Russia.
authors.forename: Maxim
authors.initials: M
authors.lastname: Eliseev
authors.affiliation: University College, Mater Misericordiae University Hospital, Dublin, Ireland.
authors.forename: Geraldine
authors.initials: G
authors.lastname: McCarthy
authors.affiliation: University of Otago Christchurch, Christchurch, New Zealand.
authors.forename: Lisa K
authors.initials: LK
authors.lastname: Stamp
authors.affiliation: Hospital Universitario Cruces and BioCruces Health Research Institute, Vizcaya, Spain.
authors.forename: Fernando
authors.initials: F
authors.lastname: Perez-Ruiz
authors.affiliation: Hospital General Universitario de Elda, Alicante, Spain.
authors.forename: Francisca
authors.initials: F
authors.lastname: Sivera
authors.affiliation: University of Paris Diderot, Sorbonne Paris Cité, UFR de Médecine, INSERM, UMR 1132, Hôpital Lariboisière, AP-HP, Paris, France.
authors.forename: Hang-Korng
authors.initials: HK
authors.lastname: Ea
authors.affiliation: Amsterdam Rheumatology Immunology Center, Westfries Gasthuis, Hoorn, The Netherlands.
authors.forename: Martijn
authors.initials: M
authors.lastname: Gerritsen
authors.affiliation: Italian Society for Rheumatology, Milan, Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: Scire
authors.affiliation: University and IRCCS Policlinico S. Matteo Foundation, Pavia, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Cavagna
authors.affiliation: Taichung Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Taiwan.
authors.forename: Chingtsai
authors.initials: C
authors.lastname: Lin
authors.affiliation: Taichung Veterans' General Hospital, Taichung, Taiwan.
authors.forename: Yin-Yi
authors.initials: YY
authors.lastname: Chou
authors.affiliation: University Hospital Carl Gustav Carus, Dresden, Germany.
authors.forename: Anne Kathrin
authors.initials: AK
authors.lastname: Tausche
authors.affiliation: Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Ana Beatriz
authors.initials: AB
authors.lastname: Vargas-Santos
authors.affiliation: Rijnstate Hospital, Arnhem, The Netherlands.
authors.forename: Matthijs
authors.initials: M
authors.lastname: Janssen
authors.affiliation: China Medical University and China Medical University Hospital, Taichung, Taiwan.
authors.forename: Jiunn-Horng
authors.initials: JH
authors.lastname: Chen
authors.affiliation: Copenhagen University Hospital, Glostrup, Denmark.
authors.forename: Ole
authors.initials: O
authors.lastname: Slot
authors.affiliation: University of Genoa, Genoa, Italy.
authors.forename: Marco A
authors.initials: MA
authors.lastname: Cimmino
authors.affiliation: Diakonhjemmet Hospital, Oslo, Norway.
authors.forename: Till
authors.initials: T
authors.lastname: Uhlig
authors.affiliation: Boston University School of Medicine, Boston, Massachusetts.
authors.forename: Tuhina
authors.initials: T
authors.lastname: Neogi
mesh_terms: D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D005260:Female; D006073:Gout / Q000145:classification* / Q000175:diagnosis; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis