Table 2.

Feature	Adults (18 years+) with severe asthma		Children (6–17 years) with severe asthma
	Observation {versus nonsevere asthma)	Reference	Observation (versus nonsevere asthma)	Reference
Exacerbation severity	Frequency emergency department visits and hospitalizations with ~30% hospitalized in the previous year; 20–25% with lifetime history of intubation	[3]	Frequent emergency department visits and hospitalizations with ~55% hospitalization in the previous year; 10–15% with lifetime history of intubation	[2,42]
Allergic sensitization	Varying degrees of atopy according to age of asthma onset and phenotype cluster	[3,20▪▪]	Highly atopic with increased peripheral blood eosinophilia, aeroallergen sensitivity, and elevated serum IgE concentrations	[2,42.44▪▪]
Exhaled nitric oxide	Not distinguishing overall but associated with exacerbations in a selected phenotype	[3,45▪]	Sustained elevations	[2]
Airflow limitation	Moderate-to-severe airflow limitation, often with incomplete reversal after bronchodilation	[3,20▪▪,46]	Some (mild) airflow limitation with near-complete reversal after bronchodilation; significant acceleration of airflow limitation in some adolescents after puberty	[2,42,48▪▪]
Air trapping	Increased air trapping (increased RV/TLC) at the same threshold of airflow limitation (FEV1/FVC)	[46]	Increased air trapping (increased RV/TLC) at baseline; reversible in girls but persistent in boys	[2,47▪▪]

FEV₁, forced expiratory volume in 1 s; FVC, forced vital capacity; RV/TLC, ratio of residual volume to total lung capacity.