title: Validation of potential classification criteria for systemic sclerosis.
abstract: OBJECTIVE
  Classification criteria for systemic sclerosis (SSc; scleroderma) are being updated jointly by the American College of Rheumatology and European League Against Rheumatism. Potential items for classification were reduced to 23 using Delphi and nominal group techniques. We evaluated the face, discriminant, and construct validity of the items to be further studied as potential criteria.
  
  
  METHODS
  Face validity was evaluated using the frequency of items in patients sampled from the Canadian Scleroderma Research Group, 1000 Faces of Lupus, and the Pittsburgh, Toronto, Madrid, and Berlin connective tissue disease (CTD) databases. Patients with SSc (n = 783) were compared to 1,071 patients with diseases similar to SSc (mimickers): systemic lupus erythematosus (n = 499), myositis (n = 171), Sjögren's syndrome (n = 95), Raynaud's phenomenon (RP; n = 228), mixed CTD (n = 29), and idiopathic pulmonary arterial hypertension (PAH; n = 49). Discriminant validity was evaluated using odds ratios (ORs). For construct validity, empirical ranking was compared to expert ranking.
  
  
  RESULTS
  Compared to mimickers, patients with SSc were more likely to have skin thickening (OR 427); telangiectasias (OR 91); anti-RNA polymerase III antibody (OR 75); puffy fingers (OR 35); finger flexion contractures (OR 29); tendon/bursal friction rubs (OR 27); anti-topoisomerase I antibody (OR 25); RP (OR 24); fingertip ulcers/pitting scars (OR 19); anticentromere antibody (OR 14); abnormal nailfold capillaries (OR 10); gastroesophageal reflux disease symptoms (OR 8); antinuclear antibody, calcinosis, dysphagia, and esophageal dilation (all OR 6); interstitial lung disease/pulmonary fibrosis (OR 5); and anti-PM-Scl antibody (OR 2). Reduced carbon monoxide diffusing capacity, PAH, and reduced forced vital capacity had ORs of <2. Renal crisis and digital pulp loss/acroosteolysis did not occur in SSc mimickers (OR not estimated). Empirical and expert ranking were correlated (Spearman's ρ = 0.53, P = 0.01).
  
  
  CONCLUSIONS
  The candidate items have good face, discriminant, and construct validity. Further item reduction will be evaluated in prospective SSc and mimicker cases.
authors: Toronto Western Hospital, Mount Sinai Hospital, and University of Toronto, Toronto, Ontario, Canada. Sindhu.Johnson@uhn.on.ca
authors: Sindhu R
authors: SR
authors: Johnson
authors: Jaap
authors: J
authors: Fransen
authors: Dinesh
authors: D
authors: Khanna
authors: Murray
authors: M
authors: Baron
authors: Frank
authors: F
authors: van den Hoogen
authors: Thomas A
authors: TA
authors: Medsger
authors: Christine A
authors: CA
authors: Peschken
authors: Patricia E
authors: PE
authors: Carreira
authors: Gabriela
authors: G
authors: Riemekasten
authors: Alan
authors: A
authors: Tyndall
authors: Marco
authors: M
authors: Matucci-Cerinic
authors: Janet E
authors: JE
authors: Pope
mesh_terms: D000328:Adult; D001323:Autoantibodies / Q000276:immunology; D015331:Cohort Studies; D004264:DNA Topoisomerases, Type I / Q000276:immunology; D006801:Humans; D011928:Raynaud Disease / Q000145:classification / Q000175:diagnosis / Q000276:immunology; D015203:Reproducibility of Results; D012595:Scleroderma, Systemic / Q000145:classification* / Q000175:diagnosis / Q000276:immunology; D012859:Sjogren's Syndrome / Q000145:classification / Q000175:diagnosis / Q000276:immunology
chemical_list: D001323:Autoantibodies; D004264:DNA Topoisomerases, Type I