2 Clinical need and practice
2.1 Asthma is a chronic disorder of the airways, caused primarily by inflammatory processes and constriction of the smooth muscle in airway walls (bronchoconstriction). It is characterised by airflow obstruction and increased responsiveness of the airways to various stimuli. Symptoms include recurring episodes of wheezing, breathlessness, chest tightness and coughing. Typical asthma symptoms tend to be variable, intermittent and worse at night. Asthma is commonly triggered by viral respiratory infections, exercise, smoke, cold, and allergens such as pollen, mould, animal fur and the house dust mite.
2.2 It is estimated that there are 5.2 million people with asthma in the UK, of whom approximately 2.9 million are women and girls and 2.3 million are men and boys. This includes 0.7 million people older than 65 years and 0.6 million teenagers. The Health Survey for England (2001) estimated the lifetime prevalence of diagnosed asthma to be 16% in women and 13% in men. The 1998 figures from the General Practice Research Database, which sampled 211 general practices in England and Wales, estimated the age-standardised prevalence of treated asthma to be 7% in men and 8% in women. Mortality from asthma is rare (1266 asthma-related deaths were reported in 2004).
2.3 Asthma is diagnosed on the basis of symptoms and objective tests of lung function (such as peak expiratory flow rate [PEF] and forced expiratory volume in the first second [FEV1]) and percentage predicted FEV1 (calculated as a percentage of the predicted FEV1 for a person of the same height, sex and age without diagnosed asthma). Variability of PEF and FEV1, either spontaneously or in response to therapy, is a characteristic feature of asthma. The severity of asthma is judged according to symptoms and the amount of medication required to control the symptoms, and is based on current British guidelines for the management of asthma from the British Thoracic Society (BTS) and Scottish Intercollegiate Guidelines Network (SIGN).
2.4 Asthma usually develops in childhood but may start at any age. There is no cure for asthma, although people may experience long periods of remission. Poorly controlled asthma can have a significant impact on the quality of life of the affected person and their family. However, there may be variation in an individual's perception of the symptoms and how he or she adapts to the condition over time. Clinical measures such as lung function may not correlate with an individual's quality of life scores, but if asthma is well controlled, near-maximal scores on quality of life instruments can be achieved.
2.5 Asthma management aims to control symptoms (including nocturnal symptoms and exercise-induced asthma), prevent exacerbations and achieve the best possible lung function, with minimal side effects of treatment. The BTS/SIGN guidelines recommend a stepwise approach to treatment in both adults and children. Treatment is started at the step most appropriate to the initial severity of the asthma, with the aim of achieving early control of symptoms and optimising respiratory function. Control is maintained by stepping up treatment as necessary and stepping down when control is good.
2.6 Mild intermittent asthma (step 1) is treated with inhaled short-acting beta‑2 agonists (SABAs), as required. The introduction of regular preventer therapy with ICSs (step 2) should be considered when a person has had exacerbations of asthma in the previous 2 years, is using inhaled SABAs three times a week or more, is symptomatic three times a week or more, or is waking at night once a week because of asthma. Add-on therapy (step 3) involves the introduction of an additional therapy, the first choice of which is an inhaled LABA. Alternatives include orally administered leukotriene receptor antagonists, theophyllines and slow-release beta-2 agonist tablets, or increasing the dose of ICS. At step 4, further interventions may be considered if control remains inadequate on a dose of ICS that is equivalent to 800 micrograms per day of beclometasone dipropionate in combination with a LABA, or following an unsuccessful trial of a LABA. Options include increasing the dose of the ICS to 2000 micrograms beclometasone dipropionate equivalent per day or adding a leukotriene antagonist, a theophylline or a slow-release beta‑2 agonist tablet. At step 5, continuous or frequent courses of oral corticosteroids are introduced. The majority of people with asthma are treated at steps 1, 2 or 3.
2.7 Asthma exacerbations (or asthma attacks) are acute episodes of a progressive increase in shortness of breath, cough, wheezing or chest tightness, or a combination of symptoms. Exacerbations lead to the consumption of additional medications or to patient-initiated healthcare consultations, often in accident and emergency departments. Severe exacerbations can be life threatening. Minor exacerbations may be treated by the individual using high doses of inhaled SABAs, although a short course of systemic corticosteroids is often also needed.
 The British Thoracic Society and Scottish Intercollegiate Guidelines Network (2003; updated 2005) British Guideline on the Management of Asthma: a national clinical guideline. SIGN Guideline No. 63. Edinburgh: Scottish Intercollegiate Guidelines Network.