title: A combined pulmonary function and emphysema score prognostic index for staging in Chronic Obstructive Pulmonary Disease.
abstract: BACKGROUND
  Chronic Obstructive Pulmonary Disease (COPD) is characterized by high morbidity and mortality. Lung computed tomography parameters, individually or as part of a composite index, may provide more prognostic information than pulmonary function tests alone.
  
  
  OBJECTIVE
  To investigate the prognostic value of emphysema score and pulmonary artery measurements compared with lung function parameters in COPD and construct a prognostic index using a contingent staging approach.
  
  
  METHODS
  Predictors of mortality were assessed in COPD outpatients whose lung computed tomography, spirometry, lung volumes and gas transfer data were collected prospectively in a clinical database. Univariate and multivariate Cox proportional hazard analysis models with bootstrap techniques were used.
  
  
  RESULTS
  169 patients were included (59.8% male, 61.1 years old; Forced Expiratory Volume in 1 second % predicted: 40.5±19.2). 20.1% died; mean survival was 115.4 months. Age (HR = 1.098, 95% Cl = 1.04-1.252) and emphysema score (HR = 1.034, 95% CI = 1.007-1.07) were the only independent predictors of mortality. Pulmonary artery dimensions were not associated with survival. An emphysema score of 55% was chosen as the optimal threshold and 30% and 65% as suboptimals. Where emphysema score was between 30% and 65% (intermediate risk) the optimal lung volume threshold, a functional residual capacity of 210% predicted, was applied. This contingent staging approach separated patients with an intermediate risk based on emphysema score alone into high risk (Functional Residual Capacity ≥210% predicted) or low risk (Functional Residual Capacity <210% predicted). This approach was more discriminatory for survival (HR = 3.123; 95% CI = 1.094-10.412) than either individual component alone.
  
  
  CONCLUSIONS
  Although to an extent limited by the small sample size, this preliminary study indicates that the composite Emphysema score-Functional Residual Capacity index might provide a better separation of high and low risk patients with COPD, than other individual predictors alone.
authors.affiliation: NIHR Respiratory Biomedical Research Unit at Royal Brompton and Harefield NHS Foundation Trust and Imperial College, London, United Kingdom.
authors.forename: Afroditi K
authors.initials: AK
authors.lastname: Boutou
authors.affiliation: NIHR Respiratory Biomedical Research Unit at Royal Brompton and Harefield NHS Foundation Trust and Imperial College, London, United Kingdom.
authors.forename: Arjun
authors.initials: A
authors.lastname: Nair
authors.affiliation: Department of Radiology, Chelsea and Westminster NHS Foundation Trust, London, United Kingdom.
authors.forename: Dariush
authors.initials: D
authors.lastname: Douraghi-Zadeh
authors.affiliation: Department of Radiology, Imperial College Healthcare NHS Trust, London, United Kingdom.
authors.forename: Ranbir
authors.initials: R
authors.lastname: Sandhu
authors.affiliation: NIHR Respiratory Biomedical Research Unit at Royal Brompton and Harefield NHS Foundation Trust and Imperial College, London, United Kingdom.
authors.forename: David M
authors.initials: DM
authors.lastname: Hansell
authors.affiliation: NIHR Respiratory Biomedical Research Unit at Royal Brompton and Harefield NHS Foundation Trust and Imperial College, London, United Kingdom.
authors.forename: Athol U
authors.initials: AU
authors.lastname: Wells
authors.affiliation: NIHR Respiratory Biomedical Research Unit at Royal Brompton and Harefield NHS Foundation Trust and Imperial College, London, United Kingdom.
authors.forename: Michael I
authors.initials: MI
authors.lastname: Polkey
authors.affiliation: NIHR Respiratory Biomedical Research Unit at Royal Brompton and Harefield NHS Foundation Trust and Imperial College, London, United Kingdom.
authors.forename: Nicholas S
authors.initials: NS
authors.lastname: Hopkinson
mesh_terms: D016001:Confidence Intervals; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D016016:Proportional Hazards Models; D029424:Pulmonary Disease, Chronic Obstructive / Q000401:mortality / Q000503:physiopathology*; D011656:Pulmonary Emphysema / Q000401:mortality / Q000503:physiopathology*; D012129:Respiratory Function Tests; D012307:Risk Factors