COPD	Chronic Obstructive Pulmonary Disease
A1ATD	Alpha-1 Antitrypsin Deficiency (alternative notation)
FEV1	Forced Expiratory Volume in 1 Second
FVC	Forced Vital Capacity
FEV1/FVC	Ratio of Forced Expiratory Volume in 1 Second to Forced Vital Capacity
DLCO	Diffusing Capacity for Carbon Monoxide
NLR	Neutrophil-to-Lymphocyte Ratio
FeNO	Fractional Exhaled Nitric Oxide
TNF-α	Tumor Necrosis Factor-alpha
IL-8	Interleukin-8
MMPs	Matrix Metalloproteinases
mMRC	Modified Medical Research Council Dyspnea Scale
CAT	COPD Assessment Test
GOLD	Global Initiative for Chronic Obstructive Lung Disease
KOCOSS	Korea COPD Subgroup Study
VGDF	Vapors, Gases, Dusts, and Fumes
PM2.5	Particulate Matter ≤ 2.5 μm
PM10	Particulate Matter ≤ 10 μm
NOx	Nitrogen Oxides
NO2	Nitrogen Dioxide
CO	Carbon Monoxide
HIV	Human Immunodeficiency Virus
TB	Tuberculosis
CD8+ T cells	Cluster of Differentiation 8 Positive T Lymphocytes
OR	Odds Ratio
CI	Confidence Interval
BMI	Body Mass Index
CT	Computed Tomography
QoL	Quality of Life