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Definition

Home Severe Asthma Definition

Severe Asthma Definition

Following confirmation of a diagnosis of asthma and after comorbidities have been addressed, severe asthma is defined as ‘‘asthma which requires treatment with high dose inhaled corticosteroids (ICS) plus a second controller (and/or systemic corticosteroids) to prevent it from becoming ‘uncontrolled’ or which remains ‘uncontrolled’ despite this therapy.’’ – (Chung et al. 2014)

Severe Asthma is Asthma that remains...

Uncontrolled...
Despite treatable factors having been addressed...
And maximal inhaled therapy being taken regularly
Uncontrolled...
  • Poor symptom control
  • Frequent severe exacerbations / flare-ups / attacks
  • Serious exacerbations (e.g. hospitalisation, ICU stay or mechanical ventilation)
  • Airflow limitation or
  • Controlled asthma that worsens on tapering of corticosteroid treatment
Despite treatable factors having been addressed...
  • Treatment adherence
  • Inhaler device technique
  • Self-monitoring
  • Trigger avoidance
  • Comorbidities identified and managed
And maximal inhaled therapy being taken regularly
  • High-dose inhaled corticosteroids (ICS) (e.g. beclomethasone >1000, budesonide >800) AND
  • Long-acting beta agonists (LABA) or other controller

Having severe asthma symptoms does not necessarily mean that the person has “severe asthma”. To explain this, it is important to understand two key concepts in asthma management: asthma control and asthma severity.

Asthma Control
Asthma Severity
Asthma Control
ASTHMA CONTROL means the extent to which the features of asthma have been reduced or removed. There are two components:

  • ‘symptom control’, meaning how often the person has symptoms, night waking and limited activity due to asthma
  • the person’s risk of having adverse outcomes in the future, particularly asthma flare-ups, accelerated decline in lung function, or medication side-effects.

Well-controlled asthma means that asthma symptoms are infrequent (twice a week or less), there is no night waking due to asthma, no limitation of normal activities, and the person is at a low risk of flare-ups.

Uncontrolled asthma, as well as burdening the patient with symptoms, can result in frequent flare-ups / attacks, adverse reactions to medication and chronic morbidity. In Australia, about 45% of adults with asthma have uncontrolled symptoms, and around one quarter have had a flare-up in the past year (Reddel et al. 2015). Some patients have risk factors that increase their chance of flare-ups, even if they have few symptoms (Bateman et al. 2015, Loymans et al. 2016, GINA 2017).

Asthma Severity
ASTHMA SEVERITY does not mean how bad the asthma symptoms are, but how much treatment is needed to keep asthma well-controlled.

Mild asthma is asthma that can be well-controlled with a low-dose inhaled corticosteroid preventer.

Severe asthma (also called ‘severe refractory asthma’) is asthma that remains uncontrolled (symptoms and/or flare-ups) despite treatable factors having been addressed and maximal inhaled therapy being taken, or, in a few patients, remains well-controlled only while high dose treatment is being taken. ‘Refractory’ means that the person’s asthma does not respond as well to treatment as it does for most people. For more information, see Diagnosis.

For strategic reasons in developing countries, the World Health Organisation (WHO) defines an additional category called “untreated severe asthma”. This refers to people with severe symptoms resulting from undiagnosed asthma, or unavailability of treatments (Bousquet et al. 2010). When inhaled corticosteroids are made available, asthma morbidity is dramatically reduced (Cerci Neto et al. 2008).

Most people with asthma experience mild to moderate symptoms, and most can respond well to standard preventer therapies (inhaled corticosteroids with or without long-acting beta2-agonists (LABAs)). However, some people continue to experience poor symptom control or flare-ups, despite being prescribed maximum doses of preventer medication. This is called ‘difficult-to-treat asthma’. For many of these patients, this is because of problems that can be treated, including not using their preventer inhaler correctly or not taking it regularly, or because they also have other conditions such as sinusitis or obesity (called ‘comorbidities’) that can make asthma symptoms worse. Sometimes, it is because they don’t have asthma, but their respiratory symptoms are due to another condition such as cardiac disease or vocal cord dysfunction.

However, no asthma is the same. Some people with asthma continue to have frequent symptoms, or frequent flare-ups (or both), despite the diagnosis having been checked, other conditions having been treated, and despite them regularly taking maximum doses of inhaled preventer medication. This is called ‘severe asthma’ or ‘severe treatment-refractory asthma’. ‘Refractory’ means that it does not respond as well to normal inhaled preventer treatment as it does for most people.

severe asthma definition infographic, difficult to treat asthma and severe refractory asthma
International severe asthma guidelines were published in 2014. The formal definition of severe asthma in these guidelines is: “Asthma which requires treatment with guidelines suggested medications for GINA steps 4–5 asthma (high dose inhaled corticosteroid (ICS) and long acting beta agonist (LABA) or leukotriene modifier/theophylline) for the previous year or systemic corticosteroids for ≥50% of the previous year to prevent it from becoming “uncontrolled” or which remains “uncontrolled“ despite this therapy”. – International ERS/ATS Guidelines 2014 (Chung et al. 2014). In these guidelines, the definition of “uncontrolled” asthma includes persistent symptoms, frequent or severe exacerbations, and/or low lung function.

The ERS/ATS severe asthma guidelines also emphasise that “Inherent in the definition of severe asthma is the exclusion of individuals who present with ‘‘difficult’’ asthma in whom appropriate diagnosis and/or treatment of confounders vastly improves their current condition” (Chung et al. 2014). In population studies, it is therefore not possible at present to identify patients with severe asthma, as severe asthma is a diagnosis of exclusion.

Within the clinic, it can be difficult to differentiate between these patient subsets (particularly difficult-to-treat and treatment-refractory). It is important to recognise that differences exist, as symptoms may result from differing underlying causes, which in turn require different intervention approaches. For more information, see Diagnosis.

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Last Updated on October 27, 2022

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  • Overview
  • Definition
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  • Severe Asthma Attacks / Exacerbations / Flare-ups
  • Asthma Phenotypes

What is Severe Asthma?

It is asthma that remains uncontrolled despite treatable factors having been addressed and maximal inhaled therapy being taken regularly.

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