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Table 1 Description of phenotypic variables

From: Analyzing networks of phenotypes in complex diseases: methodology and applications in COPD

Variables (abbreviation)

Descriptions/Comments

FEV1 (% predicted FEV1)

Observed FEV1 (liters)/predicted FEV1 (liters), with predicted valued from Hankinson reference equations

Emphysema (Emph)

% Emphysema at -950 Hounsfield units(HU)

Emphysema Distribution (EmphDist)

Log ratio of emphysema at -950 HU in the upper 1/3 of lung fields compared to the lower 1/3 of lung fields

Gas Trapping (GasTrap)

Air trapping at -856HU on expiratory chest CT scan

Airway Wall Area (Pi10)

Square root of the wall area of a hypothetical 10 mm internal perimeter airway

Exacerbation frequency (ExacerFreq)

Number of COPD exacerbations during the year before study enrollment

Six minute walk distance (6MWD)

Measure of exercise capacity

BMI

Body Mass Index

Age

In years

Pack-Years (PackYear)

One pack-year is defined as smoking one pack (20 cigarettes) per day for one year