title: A multidimensional index and staging system for idiopathic pulmonary fibrosis.
abstract: BACKGROUND
  Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic lung disease with an overall poor prognosis. A simple-to-use staging system for IPF may improve prognostication, help guide management, and facilitate research.
  
  
  OBJECTIVE
  To develop a multidimensional prognostic staging system for IPF by using commonly measured clinical and physiologic variables.
  
  
  METHODS
  A clinical prediction model was developed and validated by using retrospective data from 3 large, geographically distinct cohorts.
  
  
  METHODS
  Interstitial lung disease referral centers in California, Minnesota, and Italy.
  
  
  METHODS
  228 patients with IPF at the University of California, San Francisco (derivation cohort), and 330 patients at the Mayo Clinic and Morgagni-Pierantoni Hospital (validation cohort).
  
  
  METHODS
  The primary outcome was mortality, treating transplantation as a competing risk. Model discrimination was assessed by the c-index, and calibration was assessed by comparing predicted and observed cumulative mortality at 1, 2, and 3 years.
  
  
  RESULTS
  Four variables were included in the final model: gender (G), age (A), and 2 lung physiology variables (P) (FVC and Dlco). A model using continuous predictors (GAP calculator) and a simple point-scoring system (GAP index) performed similarly in derivation (c-index of 70.8 and 69.3, respectively) and validation (c-index of 69.1 and 68.7, respectively). Three stages (stages I, II, and III) were identified based on the GAP index with 1-year mortality of 6%, 16%, and 39%, respectively. The GAP models performed similarly in pooled follow-up visits (c-index ≥71.9).
  
  
  CONCLUSIONS
  Patients were drawn from academic centers and analyzed retrospectively.
  
  
  CONCLUSIONS
  The GAP models use commonly measured clinical and physiologic variables to predict mortality in patients with IPF.
authors.affiliation: Department of Medicine, University of California, San Francisco, 505 Parnassus Avenue, Box 0111, San Francisco, CA 94143, USA. brett.ley@ucsf.edu
authors.forename: Brett
authors.initials: B
authors.lastname: Ley
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Ryerson
authors.forename: Eric
authors.initials: E
authors.lastname: Vittinghoff
authors.forename: Jay H
authors.initials: JH
authors.lastname: Ryu
authors.forename: Sara
authors.initials: S
authors.lastname: Tomassetti
authors.forename: Joyce S
authors.initials: JS
authors.lastname: Lee
authors.forename: Venerino
authors.initials: V
authors.lastname: Poletti
authors.forename: Matteo
authors.initials: M
authors.lastname: Buccioli
authors.forename: Brett M
authors.initials: BM
authors.lastname: Elicker
authors.forename: Kirk D
authors.initials: KD
authors.lastname: Jones
authors.forename: Talmadge E
authors.initials: TE
authors.lastname: King
authors.forename: Harold R
authors.initials: HR
authors.lastname: Collard
mesh_terms: D000367:Age Factors; D005260:Female; D006801:Humans; D054990:Idiopathic Pulmonary Fibrosis / Q000175:diagnosis* / Q000401:mortality / Q000503:physiopathology / Q000601:surgery; D008168:Lung / Q000503:physiopathology; D016040:Lung Transplantation; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D011379:Prognosis; D011653:Pulmonary Diffusing Capacity; D012189:Retrospective Studies; D018570:Risk Assessment; D014797:Vital Capacity