Originally published: June 2018

Key learning points

  • Diagnosis of asthma remains challenging but it is helpful to use the code suspected asthma until diagnosis can be confirmed
  • Spirometry is the preferred initial diagnostic test but normal spirometry does not rule out an asthma diagnosis
  • Inhaled corticosteroids remain the cornerstone of asthma management and are recommended for all patients with a confirmed diagnosis

Introduction

The British Thoracic Society (BTS) and Scottish Intercollegiate Guidelines Network (SIGN) guideline on the management of asthma1 is often referred to as a ‘living guideline’. It is reviewed and updated regularly and the most current version is considered to be the standard upon which to base asthma management in the UK.

The 2016 version introduced a number of fundamental changes, particularly in the sections on diagnosis and pharmacological management. Whilst this article will focus on those sections, it is important to note that other sections, including asthma in pregnancy and acute asthma have also been updated.

Diagnosis

Diagnosing asthma is difficult, there is no single test that can confirm or refute an asthma diagnosis in every person. The reason for this is that asthma is a variable condition; levels of inflammation and degrees of airflow limitation vary depending on factors such as time of day and response to aggravating triggers such as allergens, infections or irritants. Therefore, people with asthma who feel well and are symptom-free at the time of testing may have normal lung function.

In response to calls for improved levels of accuracy in the diagnosis of asthma, the current BTS/SIGN guideline offers a clear pathway for clinicians to follow (see Figure 1).

Figure 1: Diagnostic algorithm

In patients presenting with respiratory symptoms suggestive of asthma, a structured clinical assessment should be undertaken to determine the likelihood or probability of asthma. History of symptoms and when they occur is key to diagnosis; symptoms of asthma typically vary, they are often worse during the night or early in the morning and they tend to occur in response to more than one trigger.

Until asthma diagnosis is confirmed the code suspected asthma should be used.

Where, based upon the structured clinical assessment, the probability of asthma is high, commence patients on a trial of asthma treatment such as low dose inhaled corticosteroid (ICS) twice daily. After six to eight weeks, review patients to assess response. Tools such as the Asthma Control Test are useful markers of response although as they are based on patient perceptions, they tend to be subjective. Ideally, response will also be measured more objectively using spirometry or peak flow to demonstrate reversibility.

Response to ICS is expected if a patient has asthma, provided it was taken correctly as prescribed with a good inhaler technique.

In cases of low probability of asthma it is wise to consider an alternative diagnosis and the pathway will depend on the individual patient.

An outcome of intermediate probability of asthma following a structured clinical assessment is common and the next steps require greater consideration. Further investigations are required and spirometry is the preferred initial test.

Spirometry should be performed and interpreted to quality-assured standards2 and if bronchodilator reversibility >400mls can be demonstrated, the diagnosis of asthma is highly likely. Reversibility >200mls with at least 12% improvement is significant and increases the probability of asthma further.

Normal spirometry does not rule out a diagnosis of asthma – and evidence of reversibility spirometry alone does not make the diagnosis of asthma

Where spirometry cannot be performed or is inconclusive, further investigations are necessary. Peak expiratory flow rate (PEFR) charting, carried out over a period of two to four weeks can demonstrate diurnal variation, which is typical in asthma. However, this method has its limitations, not least because studies have shown patient concordance to be poor.3

Measurement of fractional exhaled nitric oxide (FeNO) levels to identify inflammatory biomarkers can be undertaken. Raised levels indicate inflammation in the airways and increase the probability of asthma; however, there are confounding factors that can affect results. FeNO measurement is limited by its current lack of availability in primary care.4

Pharmacological management

In patients with a confirmed diagnosis of asthma, regular ICS treatment is necessary to control inflammation and prevent symptoms/exacerbations. The Step 1 of previous guidelines, where patients with infrequent symptoms are treated with only a short acting bronchodilator as needed, is no longer recommended.

The message is very clear – asthma is caused by inflammation in the airways and must be treated accordingly with inhaled corticosteroids

Rather than numbered steps, treatment is now guided in logical phases of increasing and decreasing treatment in response to clinical need. This approach continues to reflect the variable nature of asthma over a life course.

Additional treatment is necessary in patients whose asthma is poorly controlled on low dose ICS. It is essential to ensure patients are taking their existing asthma treatment regularly as prescribed and that inhaler technique is good before adding further treatment. Long acting beta-agonist bronchodilators (LABA) are the recommended initial add-on therapy; these must always be taken in addition to ICS. To avoid LABA being taken as monotherapy both are prescribed in a single combination inhaler.

Where response to the addition of LABA is poor, the LABA is stopped and the ICS increased to medium dose. If the response to LABA is partial, additional add-on therapy is recommended and options include the addition of anti-leukotreines (LTRA), theophylline or a long acting muscarinic antagonist (LAMA). The ICS dose can also be increased to medium dose but beyond this specialist referral is necessary. It is important to note that patients with asthma not responding to such levels of treatment require further specialist investigation.

High dose ICS or regular oral corticosteroids should only be initiated in specialist care and the use of biological agents (eg omalizumab) can only be initiated within an approved secondary care environment.

Conclusion

The current British guideline for the management of asthma offers evidence-based guidance in a clear and logical manner that is easily applied to clinical practice. Diagnosis of asthma remains challenging but it is helpful to use the code suspected asthma until diagnosis can be confirmed. History taking is fundamental to determination of probability, which provides a solid foundation to achieving accurate diagnosis. Spirometry is the preferred initial diagnostic test but normal spirometry does not rule out an asthma diagnosis. ICS remains the cornerstone of asthma management and are recommended for all patients with a confirmed diagnosis. Treatment adjustment is driven by patients’ level of asthma control and it is imperative to ensure adherence and inhaler technique are good before any increases are made. Patients who are not well-controlled on medium dose ICS plus add on treatments need to be referred for specialist care.

Ms Viv Marsh is an asthma nurse specialist at Dudley CCG and education lead at Education for Health.

Further reading
A wide range of education and training options to promote the safe and effective assessment and management of patients with asthma are available at Education for Health.

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