Asthma is a chronic inflammatory respiratory disease. It can affect people of any age, but often starts in childhood. Asthma is a variable disease which can change throughout a person's life, throughout the year and from day to day. It is characterised by attacks (also known as exacerbations) of breathlessness and wheezing, with the severity and frequency of attacks varying from person to person. The attacks are associated with variable airflow obstruction and inflammation within the lungs, which if left untreated can be life-threatening, however with the appropriate treatment can be reversible.

In 2018, the Global Asthma report estimated that asthma affects 339 million people worldwide. It is the most common chronic condition to affect children, and in the UK approximately 5.4 million people (1.1 million children and 4.3 million adults) currently get treatment for asthma (Asthma UK).

The causes of asthma are not well understood. A number of risk factors are associated with the condition, often in combination. These influences can be genetic (the condition clusters in families) and/or environmental (such as inhalation of allergens or chemical irritants). Occupational causes of asthma in adults are often under-recognised.

Diagnosis and monitoring

There is currently no gold standard test available to diagnose asthma; diagnosis is principally based on a thorough history taken by an experienced clinician. Studies of adults diagnosed with asthma suggest that up to 30% do not have clear evidence of asthma. Some may have had asthma in the past, but it is likely that many have been given an incorrect diagnosis. Conversely, other studies suggest that asthma may be underdiagnosed in some cases.

The diagnosis recommendations will improve patient outcomes and will be cost effective to the NHS in the long-term; NICE's cost impact assessment projects a saving of approximately £12 million per year in England, before implementation costs.

Initial clinical assessment should include questions about symptoms (wheezing, cough, breathing and chest problems) and any personal or family history of allergies, atopic disorders or asthma. Various tests can be used to support a diagnosis, but there is no single test that can definitively diagnose asthma.

A number of methods and assessments are available to determine the likelihood of asthma. These include measuring airflow obstruction (spirometry and peak flow) and assessment of reversibility with bronchodilators, with both methods being widely used in current clinical practice. However, normal results do not exclude asthma and abnormal results do not always mean it is asthma, because they could be indicators of other respiratory diseases or spurious readings.

Testing for airway inflammation is increasingly used as a diagnostic strategy in clinical practice. This includes measuring fractional exhaled nitric oxide (FeNO).

Other diagnostic strategies include blood or skin prick tests to detect allergic reactions to environmental influences, exercise tests to detect evidence of bronchoconstriction, and measures of airway hyperreactivity such as histamine/methacholine or mannitol challenge tests. However, it is debatable which test or measure, or combination of them, is the most effective to accurately diagnose asthma.

It is recognised that asthma control is suboptimal in many people with asthma. This has an impact on their quality of life, their use of healthcare services and the associated costs. Asthma control can be monitored by measuring airway obstruction or inflammation and by using validated questionnaires, but the most effective monitoring strategy is unclear.

Managing chronic asthma

The severity of asthma varies; some people have severe asthma that limits normal activities, whereas others are able to lead a relatively normal life. The illness fluctuates during the year and over time, so the level of treatment needs to be tailored to the person's current level of asthma severity. Many people with asthma, particularly children, seem to have fewer symptoms over time, and an important part of management is decreasing treatment if asthma is well controlled.

There is no cure for asthma, so management focuses on reducing exposure to known triggers if possible, relief of symptoms if there is airway narrowing, and reduction in airway inflammation by regular preventive treatment. Adherence to regular treatment reduces the risk of significant asthma attacks in most people with asthma. The focus of asthma management in recent years has been on supporting people with asthma and their healthcare professional to devise a personalised treatment plan that is effective and relatively easy to implement.

The aims of this guideline

The guideline covers children under 5, children and young people aged 5 to 16, and adults aged 17 and over with suspected or diagnosed asthma. The guideline applies to all primary, secondary and community care settings in which NHS-funded care is provided for people with asthma.

The sections on diagnosing and monitoring asthma (sections 1.1 to 1.4 and 1.13) aim to provide clear advice on effectively diagnosing people presenting with new symptoms of suspected asthma and monitoring to ensure optimum asthma control. It is not intended to be used to re‑diagnose people who already have an asthma diagnosis.

The sections on managing chronic asthma (sections 1.5 to 1.12) aim to provide clear advice for healthcare professionals and people with asthma to develop a personalised action plan. The plan should support self-management of asthma, and ensure that the person is receiving the best possible treatment for their current level of illness. It focuses on the pharmacological management of chronic asthma, in particular the treatment pathway for people with uncontrolled asthma. It also covers adherence to treatment, risk stratification and self-management.

The guideline does not cover severe, difficult-to-control asthma or the management of acute asthma attacks.

In 2018, new evidence was identified by the NICE surveillance team on increasing the dose of inhaled corticosteroids within a self-management programme in children and young people with asthma. Topic experts, including those who helped to develop the 2017 guideline, agreed that the new evidence could have an impact on the recommendations. This evidence was reviewed and the recommendations in this area updated.