Predicting survival across chronic interstitial lung disease: the ILD-GAP model

Chest. 2014 Apr;145(4):723-728. doi: 10.1378/chest.13-1474.


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.

Conclusion: 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Alveolitis, Extrinsic Allergic / complications
  • Chronic Disease
  • Connective Tissue Diseases / complications
  • Female
  • Humans
  • Idiopathic Pulmonary Fibrosis / complications
  • Lung Diseases, Interstitial / complications
  • Lung Diseases, Interstitial / mortality*
  • Male
  • Middle Aged
  • Models, Theoretical
  • Prognosis
  • Survival Rate