A combined pulmonary function and emphysema score prognostic index for staging in Chronic Obstructive Pulmonary Disease.

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.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.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.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.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

Mortality, expressed as Hazard Ratios with bias-corrected 95% confidence intervals for baseline data.

<p>Mortality, expressed as Hazard Ratios with bias-corrected 95% confidence intervals for baseline data.</p

COPD prognostic staging in high and low risk, according to the ES-FRC composite index.

<p>COPD prognostic staging in high and low risk, according to the ES-FRC composite index.</p

Characteristics of the study population.

<p>Characteristics of the study population.</p

Kaplan Meier curves for the COPD population, categorized according to A) ES optimal threshold of 55%, B) ES subthresholds of 30 and 65%, C) FRC % predicted optimal threshold of 210% and D) ES-FRC composite index.

<p>Kaplan Meier curves for the COPD population, categorized according to A) ES optimal threshold of 55%, B) ES subthresholds of 30 and 65%, C) FRC % predicted optimal threshold of 210% and D) ES-FRC composite index.</p