title: Predicting survival across chronic interstitial lung disease: the ILD-GAP model.
abstract: BACKGROUND
  Risk prediction is challenging in chronic interstitial lung disease (ILD) because of heterogeneity in disease-specific and patient-specific variables. Our objective was to determine whether mortality is accurately predicted in patients with chronic ILD using the GAP model, a clinical prediction model based on sex, age, and lung physiology, that was previously validated in patients with idiopathic pulmonary fibrosis.
  
  
  METHODS
  Patients with idiopathic pulmonary fibrosis (n=307), chronic hypersensitivity pneumonitis (n=206), connective tissue disease-associated ILD (n=281), idiopathic nonspecific interstitial pneumonia (n=45), or unclassifiable ILD (n=173) were selected from an ongoing database (N=1,012). Performance of the previously validated GAP model was compared with novel prediction models in each ILD subtype and the combined cohort. Patients with follow-up pulmonary function data were used for longitudinal model validation.
  
  
  RESULTS
  The GAP model had good performance in all ILD subtypes (c-index, 74.6 in the combined cohort), which was maintained at all stages of disease severity and during follow-up evaluation. The GAP model had similar performance compared with alternative prediction models. A modified ILD-GAP Index was developed for application across all ILD subtypes to provide disease-specific survival estimates using a single risk prediction model. This was done by adding a disease subtype variable that accounted for better adjusted survival in connective tissue disease-associated ILD, chronic hypersensitivity pneumonitis, and idiopathic nonspecific interstitial pneumonia.
  
  
  CONCLUSIONS
  The GAP model accurately predicts risk of death in chronic ILD. The ILD-GAP model accurately predicts mortality in major chronic ILD subtypes and at all stages of disease.
authors.affiliation: Department of Medicine, University of British Columbia, Vancouver, BC, Canada. Electronic address: chris.ryerson@hli.ubc.ca.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Ryerson
authors.affiliation: Department of Biostatistics, University of California, San Francisco, San Francisco, CA.
authors.forename: Eric
authors.initials: E
authors.lastname: Vittinghoff
authors.affiliation: Department of Medicine, University of California, San Francisco, CA.
authors.forename: Brett
authors.initials: B
authors.lastname: Ley
authors.affiliation: Department of Medicine, University of California, San Francisco, CA.
authors.forename: Joyce S
authors.initials: JS
authors.lastname: Lee
authors.affiliation: Department of Medicine, Stanford University, Stanford, CA.
authors.forename: Joshua J
authors.initials: JJ
authors.lastname: Mooney
authors.affiliation: Department of Radiology, University of California, San Francisco, CA.
authors.forename: Kirk D
authors.initials: KD
authors.lastname: Jones
authors.affiliation: Department of Pathology, University of California, San Francisco, CA.
authors.forename: Brett M
authors.initials: BM
authors.lastname: Elicker
authors.affiliation: Department of Medicine, University of California, San Francisco, CA.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Wolters
authors.affiliation: Department of Medicine, University of California, San Francisco, CA.
authors.forename: Laura L
authors.initials: LL
authors.lastname: Koth
authors.affiliation: Department of Medicine, University of California, San Francisco, CA.
authors.forename: Talmadge E
authors.initials: TE
authors.lastname: King
authors.affiliation: Department of Medicine, University of California, San Francisco, CA.
authors.forename: Harold R
authors.initials: HR
authors.lastname: Collard
mesh_terms: D000368:Aged; D000542:Alveolitis, Extrinsic Allergic / Q000150:complications; D002908:Chronic Disease; D003240:Connective Tissue Diseases / Q000150:complications; D005260:Female; D006801:Humans; D054990:Idiopathic Pulmonary Fibrosis / Q000150:complications; D017563:Lung Diseases, Interstitial / Q000150:complications / Q000401:mortality*; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D011379:Prognosis; D015996:Survival Rate