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Chest. 2016 Feb;149(2):491-8. doi: 10.1378/chest.15-0530. Epub 2016 Jan 12.

Idiopathic Pulmonary Fibrosis: Gender-Age-Physiology Index Stage for Predicting Future Lung Function Decline.

Author information

1
Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Michigan, Ann Arbor, MI. Electronic address: msalisbu@med.umich.edu.
2
Department of Biostatistics, University of Michigan, Ann Arbor, MI.
3
Department of Biostatistics, University of Texas MD Anderson Cancer Center, Houston, TX.
4
Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, National Jewish Health, Denver, CO.
5
Interstitial Lung Disease Unit, Royal Brompton and Harefield National Health Service Foundation Trust, London, England.
6
Pulmonary Medicine, Spectrum Health, Grand Rapids, MI.
7
Pulmonary and Critical Care Medicine, Cornell Medical College, New York, NY.
8
Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Michigan, Ann Arbor, MI.

Abstract

BACKGROUND:

Idiopathic pulmonary fibrosis is a progressive lung disease with variable course. The Gender-Age-Physiology (GAP) Index and staging system uses clinical variables to stage mortality risk. It is unknown whether clinical staging predicts future decline in pulmonary function. We assessed whether the GAP stage predicts future pulmonary function decline and whether interval pulmonary function change predicts mortality after accounting for stage.

METHODS:

Patients with idiopathic pulmonary fibrosis (N = 657) were identified retrospectively at three tertiary referral centers, and baseline GAP stages were assessed. Mixed models were used to describe average trajectories of FVC and diffusing capacity of the lung for carbon monoxide (Dlco). Multivariable Cox proportional hazards models were used to assess whether declines in pulmonary function ≥ 10% in 6 months predict mortality after accounting for GAP stage.

RESULTS:

Over a 2-year period, GAP stage was not associated with differences in yearly lung function decline. After accounting for stage, a 10% decrease in FVC or Dlco over 6 months independently predicted death or transplantation (FVC hazard ratio, 1.37; Dlco hazard ratio, 1.30; both, P ≤ .03). Patients with GAP stage 2 with declining pulmonary function experienced a survival profile similar to patients with GAP stage 3, with 1-year event-free survival of 59.3% (95% CI, 49.4-67.8) vs 56.9% (95% CI, 42.2-69.1).

CONCLUSIONS:

Baseline GAP stage predicted death or lung transplantation but not the rate of future pulmonary function decline. After accounting for GAP stage, a decline of ≥ 10% over 6 months independently predicted death or lung transplantation.

KEYWORDS:

idiopathic pulmonary fibrosis; interstitial lung disease; lung function

PMID:
26425858
PMCID:
PMC4944785
DOI:
10.1378/chest.15-0530
[Indexed for MEDLINE]
Free PMC Article
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