Table 3.

Differential diagnosis of chronic obstructive pulmonary disease and asthma

Diagnostic features	COPD	Asthma
Onset age	Usually >35 years	Typically during childhood/adolescence, but can be any age
Allergic hypersensitivity	Family/Personal history rarely a factor	Usually family/personal history
Smoking history	Often >20 pack-yearsa	Possible but not necessarily
Symptom occurrence	Chronic and persistent	Intermittent; usually symptom free
Cough	Persistent and productive	Intermittent and nonproductive
Breathlessness	Progressive and persistent	Intermittent and variable
Disease course	Progressive worsening (with exacerbations)	Stable (with exacerbations)
Nocturnal symptoms	Uncommon unless severe disease state	Common
Cause of exacerbations	Bacterial/viral respiratory tract infection	Allergens, cold air, or exercise

Spirometry determined GOLD COPD stage/asthma state	FEV1b	FEV1/FVC	FEV1b	FEV1/FVC
Mild/intermittent	≥80%	<0.70	>80%	Normalc
Moderate/mild persistent	50%–79%	<0.70	>80%	Normalc
Severe/moderate persistent	30%–49%	<0.70	60%–79%	Reduction ≤5% of normal
Very severe/severe persistent	<30% or <50% with CRF	<0.70	<60%	Reduction >5% of normal
Response to bronchodilators	Variable, PFT does not normalize but may show improvement		Rapid response and PFT may greatly improve eg, FEV1 improves >0.4 L after SAB

^aNotes: Total number of pack-years is calculated = (number of cigarettes smoked per day/20) × number of years smoking (O’Donnell et al, 2008³);

^b% of predicted value;

^cnormal FEV₁/FVC values for patients aged 8–19 years = 85%, 20–39 years = 80%, 40–59 years = 75%, and 60–80 years = 70%.³,⁴,¹⁷,²⁰,³⁷,⁴⁶,⁵⁵

Abbreviations: GOLD, Global Initiative for Chronic Obstructive Lung Disease; COPD, chronic obstructive pulmonary disease; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity; CRF, chronic respiratory failure; PFT, pulmonary function test; SAB, short-acting bronchodilator.