Asthma

Definition/diagnostic criteria Asthma is a chronic respiratory condition associated with variable airway inflammation and hyper-responsiveness. There is no gold standard diagnostic test so we must rely on a combination of clinical history, examination and objective tests.

Epidemiology 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.

Diagnosis 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. Conversely, other studies suggest that asthma may be underdiagnosed in some cases.

On their own, clinical history and examination are poor predictors of whether someone has asthma or not. The more pieces of the diagnostic jigsaw we can collect, the more likely an accurate diagnosis is reached. Recording of objective measures and responses to treatment are crucial.

Clinical features People with asthma experience intermittent symptoms (cough, wheeze, breathlessness, chest tightness) in response to specific triggers or combinations of triggers. Common triggers include allergens (including pollens), viruses, stress and hormones, cold air, exercise and inhaled irritants such as tobacco smoke or pollution. A history of recurrent chest symptoms including infections, wheeze recorded by a healthcare professional, inhaler medication and raised eosinophils levels can also be useful pointers to an underlying asthma diagnosis.

Asthma can be genetic (the condition clusters in families) and/or environmental (such as inhalation of allergens or chemical irritants). Adult onset and occupational causes of asthma are under-recognised.

Investigations To help complete the diagnostic jigsaw, evidence of variable, reversible airflow obstruction and airway inflammation is needed. Spirometry with bronchodilator reversibility and FeNO testing are recommended by NICE, with a well-performed peak flow diary if these tests are inconclusive but asthma is still suspected.

A FeNO level of 40ppb or higher means asthma is more likely in adults (35ppb in those 16 and under).

Quality assured spirometry will show an obstructive pattern with an FEV1/FVC (or VC if that is greater) below the lower limit of normal, ie, a Z-score of < – 1.645. Severity of obstruction is based on the Z-score as set out in the Table.

Following administration of a bronchodilator an improvement in FEV1 of 12% and 200 ml is positive for asthma in adults. In children an increase in FEV1 of 12% is positive for asthma.

Spirometry interpretation – Z-score thresholds for severity classification

Peak flows are easier to perform but less reliable. A value of more than 20% variability after monitoring at least twice daily for 2-4 weeks is regarded as a positive result for asthma.

Because of the variable nature of asthma, if asthma is still suspected despite normal tests they should be repeated at intervals, ideally when the patient is symptomatic.

Treatment

Identifying and preventing triggers The inflammation that leads to symptoms and increases the risk of asthma exacerbations is caused by triggers specific to the person with asthma. Common triggers should be asked about so that preventative strategies can be used. These triggers include smoking and passive smoking, indoor and outdoor pollution, damp and mould within the house, pollens and mould seasons, and contact with animals. A good history may be able to establish links between symptoms and triggers.  Viruses such as influenza are a leading cause of exacerbation so keeping up with vaccinations is essential.

Medications Asthma is primarily an inflammatory condition so treatment needs to focus on suppressing the inflammation. An preventer inhaler containing a corticosteroid (ICS) is the mainstay of treatment.

Patients should also be prescribed a reliever inhaler to treat acute asthma symptoms. Anyone requiring their reliever inhaler 3 or more times per week is likely to have untreated inflammation and require a step up in their management.

Stepping up treatment can involve prescribing a long-acting bronchodilator (in a combination ICS-LABA inhaler) or montelukast in addition to continuing ICS treatment.

There are no major differences in the recommended therapeutic strategy in adults compared with children, other than for medication doses and inhaler licenses.

There is an increasing trend towards ICS-formoterol combination inhalers which can act as a preventer and a reliever at the same time. This is known as MART: Maintenance and Reliever Therapy. MART adapts treatment to the variable nature of asthma so that any reliever use is also accompanied by an increase in inhaled corticosteroid dose to help suppress underlying inflammation.

It is crucial that inhaler technique is observed at every opportunity. Inhaler videos can be a useful adjunct to help you patient get the best out of their inhalers while minimising side effects. Where an MDI is prescribed, it should be delivered via spacer, especially in children.

Education about asthma and how to self-manage should be provided routinely at diagnosis and at every opportunity.

An asthma action plan can help patients know what to do to stay well and more-importantly what to do if they develop symptoms. Asthma+Lung UK host action plans for MART and non-MART regimes, for adults and children and in a number of common languages.

Preventing and managing exacerbations For a patient experiencing an exacerbation of their symptoms, a detailed assessment is needed to establish the cause of their symptoms (is it asthma or something mimicking asthma), any potential trigger or reasons leading to an exacerbation, and the severity of the exacerbation. Symptoms, response to reliever inhaler, peak flow and exacerbation history are key factors. Night and early morning symptoms, inability to speak full sentences, reliever not fully relieving symptoms or lasting at least 4 hours and previous admissions/life-threatening asthma are worrying features.

When assessing someone’s presentation, consider whether bronchodilator use in the last 4 hours may be giving a falsely reassuring peak flow or set of symptoms/signs.

A patient should be admitted to hospital with any life-threatening features, including PEFR less than 33% best or predicted, or oxygen saturation of less than 92%, or altered consciousness, or exhaustion, or cardiac arrhythmia, or hypotension, or cyanosis, or poor respiratory effort, or silent chest, or confusion.

Bronchodilation is important to manage the immediate symptoms however addressing the underlying inflammation is critical. An adult should be prescribed 40-50mg of prednisolone once daily for at least 5 days. All patients being treated for an asthma exacerbation should be reviewed again within 48 hours (or within 48 hours of discharge from hospital) to assess recovery, underlying asthma control and management/self-management. Reassessment is necessary if there is not full resolution of symptoms by the end of the course. Further doses of prednisolone may be needed.

Prognosis For most people with asthma, low-dose inhaled corticosteroids taken every day and with a good inhaler technique will give good asthma control.

Good asthma control is characterised by asthma symptoms or reliever use less than three times per week, no night symptoms, no limitations of activity by the asthma, and peak flow >80% of best ever peak flow (in children use the peak flow predicted for age and height).

Poor asthma control increases the risk of asthma exacerbations and asthma attacks. Poor control should prompt an assessment of the diagnosis, co-morbidities, triggers, adherence to treatment and inhaler technique. Use of six or more SABAs in 12 months has been demonstrated as an effective predictive marker of future risk for asthma exacerbations.

Anyone who has poorly controlled asthma despite regular, moderate-dose ICS, with or without montelukast or a LABA should be considered for referral to a severe asthma clinic. Other criteria for a referral include: frequent exacerbations (two or more per year) requiring oral steroids; serious exacerbations (one or more per year) requiring hospitalisation or ED attendance; and six or more SABAs in a 12-month period.

Severe asthma clinics have access to investigations and treatments (including biologics therapy) that can be life-changing for people with uncontrolled asthma.

Dr Andrew Whittamore is a GPSI in respiratory medicine in Hampshire and clinical lead at Asthma + Lung UK