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November 2008: Managing patients with difficult asthma

What new diagnostic tests are available for asthma?

When should patients with poorly controlled asthma be referred?

Should I arrange allergy testing for patients with poorly controlled asthma?

What new diagnostic tests are available for asthma?

When should patients with poorly controlled asthma be referred?

Should I arrange allergy testing for patients with poorly controlled asthma?

Asthma affects around 5.2 million people in the UK. There are more than 4.1 million GP consultations for asthma each year1 and every GP will see patients with respiratory symptoms who may have asthma, or have been diagnosed with asthma but continue to have ongoing problems.

What new diagnostic tests are available for asthma?

The diagnosis of asthma is clinical and based on variable symptoms of wheeze, cough, breathlessness and chest tightness.

A history of childhood respiratory symptoms or night-time disturbance by respiratory symptoms increases the likelihood of asthma.

A diagnosis of asthma may commit patients to lifelong therapy, so it is important to carry out objective tests to confirm diagnosis.

Spirometry, which is becoming more widely available, should become the initial investigation of choice. It is preferable to peak expiratory flow (PEF) because it allows a clearer identification of airflow obstruction and the results are less dependent on effort.

In some patients the diagnosis can remain uncertain after taking a history and performing spirometry. In these cases spirometry is again very useful. Patients with airflow obstruction should have a reversibility test with 400µg inhaled salbutamol, a 6-8 week trial of 200µg inhaled beclometasone (or equivalent) twice daily or a two-week trial of oral prednisolone 30mg daily. Confirmation of reversibility, ie a >400ml improvement in FEV1, strongly suggests a diagnosis of asthma.

Other diagnostic tests will soon be more widely available for cases where the diagnosis is unclear and spirometry does not show airflow obstruction.

Asthma is caused by inflammation within the airways, which is most often eosinophilic. A simple, non-invasive way of assessing eosinophilic airway inflammation is to measure the concentration of exhaled nitric oxide (FENO). A raised FENO of >25 parts per billion is found in almost 80% of patients with untreated asthma,2 and a low FENO concentration tends to exclude the diagnosis. Although FENO testing is still fairly expensive (the cost per test is £5.60-£10), equipment to measure FENO is becoming increasingly available and measurement is relatively simple.

It seems likely that in the near future the measurement of FENO will become much more widely available, both in hospital and primary care, to help confirm diagnosis. In addition, there is increasing evidence that measurement of FENO is closely related to a positive response to inhaled steroids, and therefore routine monitoring of FENO may make it possible to titrate the steroid dose and assess compliance.

However, in a recent study of 564 patients the addition of FENO measurement to asthma management resulted in higher doses of inhaled steroids without significant improvement in asthma control.3 Time will tell how this new measurement fits into the routine management of asthma in primary care.

Other useful diagnostic tests include exercise testing and bronchial challenge testing. Both of these tests have a high sensitivity and a negative result is a strong indication that the patient does not have asthma.

Bronchial challenge testing was formerly a complicated procedure carried out only in respiratory research units. However, newer techniques using the indirect challenge of mannitol4 will soon become more widely available.

While in the short-term bronchial challenge testing is likely to be performed in hospital respiratory clinics, in the future it is likely that these methods will also become available in primary care.

If I have a middle-aged patient with asthma who has smoked all her life, how do I know if she has COPD and how would this affect management?

Both asthma and COPD are common in patients over 50 and differentiating between the two is a common clinical problem. It is important to emphasise that the prevalence of smoking in patients with asthma is the same as in the normal population.

Patients with COPD tend to have persistent and gradually worsening symptoms of breathlessness and wheeze, which are typically worse in the early morning but does not cause night-time waking.

A normal FEV1 , on spirometry, excludes COPD although does not exclude asthma. For patients with airflow obstruction, reversibility testing should be diagnostic; those with asthma will show a >400ml improvement in FEV1, or alternatively a >15% improvement in PEF, while those with COPD will have significantly less change in lung function.

Patients with a confirmed diagnosis of asthma should be given a short-acting beta-agonist (SABA) and counselled on inhaler technique. Those using a SABA more than three times a week, or waking from sleep with respiratory symptoms one night a week or more, should start inhaled steroid therapy.

In contrast, those with COPD should be graded as ‘moderate', ‘severe' or ‘very severe' on the basis of their FEV1, see table 1, attached, and current smokers should be advised to stop smoking.5

Patients with ‘moderate COPD' should be given a SABA inhaler and those with persistent symptoms could be considered for long-acting anticholinergic therapy with tiotropium.

Patients with an FEV1 <60% who have repeated exacerbations should be considered for high-dose inhaled steroid therapy, which is best combined with long-acting

beta-agonists (LABAs). Several large studies in patients with COPD have shown that this combination can reduce the rates of exacerbations and hospital admissions and improve the quality of life for these patients.6

Those with an FEV1 <30% have very severe COPD and are usually very disabled. They should be considered for long-term oxygen therapy (LTOT), particularly if resting oxygen saturation while breathing air is <92%.

At all stages of COPD, there is increasing evidence that pulmonary rehabilitation, where available, can improve quality of life and functional activity, which can be assessed by measures such as the incremental shuttle walking test.

When should patients with poorly controlled asthma be referred?

Most patients with asthma can be managed within primary care. Patient education, particularly a written and personalised asthma action plan, is always vital in achieving good asthma control. Poor control can be defined according to the criteria set out in the Global Initiative for Asthma (GINA) guidelines, see table 2, attached.7

The asthma control test (ACT) is a simple five-question test which was originally designed for use in primary care, see figure 1, attached.8 All the questions refer to the patient's asthma control over the past four weeks. A total score of 25 indicates perfect control, 20-24 indicates that asthma may be well controlled, although further advice should be obtained, and <20 indicates that further recommendations regarding management should be made by a nurse or doctor.

Patients with persistent poor control, particularly at step four or five of the British guideline on the management of asthma9 should be referred to their local respiratory specialist clinic.

Should I arrange allergy testing for patients with poorly controlled asthma?

Allergens are well recognised triggers of asthma and it can often be useful to carry out allergy testing in patients with troublesome symptoms. Testing may identify a general allergic status or atopy, or suggest that specific triggers, eg dust mites, aggravate symptoms.

Case-control studies have reported that mould sensitisation has been associated with recurrent admission to hospital and oral steroid use.9

Allergy testing should probably be performed in all patients who have poorly controlled asthma.

When should patients with acute asthma be referred?

Despite improvements in the understanding of the underlying cell biology and also improved drug therapy and inhaler devices, acute asthma is still associated with significant mortality. Approximately 1,400 patients with asthma die each year in the UK, which equates to around one death every seven hours.1 Confidential enquiries into asthma deaths have repeatedly shown that patients and relatives often fail to appreciate the severity of symptoms, while clinical staff may fail to assess severity by objective measurements. Underuse of iv or oral steroids is also a common factor.

When assessing a patient with acute asthma, it is important to measure lung function, usually PEF, together with heart and respiratory rate and oxygen saturation by pulse oximeter. Severity of acute asthma can be graded according to lung function, see table 3, attached.10

Those with acute, severe or life-threatening asthma should be referred to hospital immediately.

Author

Dr Graham Douglas
BSc FRCPE
consultant physician, Aberdeen Royal Infirmary and Co-chair, BTS/SIGN Asthma Guideline Development Group

Figure 1: The asthma control test Table 1: Grades of COPD based on post-bronchodilator FEV1 Table 2: Levels of asthma control Table 3: Levels of severity of acute asthma exacerbations

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