Asthma: what the guideline says

The new asthma guideline from NICE, due for publication in July, aims to formalise the diagnosis of asthma to avoid the risk of overdiagnosis and overtreatment. Practice Nurse looks at the draft recommendations in detail

After decades of effort to ensure that people with asthma are diagnosed and have their treatment optimised, it now seems that the pendulum may have swung too far the other way. NICE reports that more than 1 million of the 4.1 million people in the UK who are currently being treated for asthma may have been misdiagnosed.¹

NICE says that 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.

The Institute made the claim earlier this year as it published a draft guideline – its first on asthma – covering adults, children and young people who are being investigated for suspected asthma, or who have been diagnosed with asthma and are having their condition monitored.

Yet bizarrely, NICE has also stated that 5.4 million people in the UK – including 1.1 million children – are estimated to have asthma,² thus implying that some 1.3 million people with asthma are either undiagnosed or not currently being treated.

The discrepancy may be explained by the low sensitivity and specificity of diagnosing asthma on the basis of symptoms alone – which, NICE says, can lead to a large number of false negatives and false positives. Using symptoms alone as a diagnostic test would lead to clinical harm to individuals who have asthma but who go untreated, and to those who do not have asthma but are given treatment.

Professor Mark Baker, director of clinical practice at NICE said: ‘Asthma is a long-term incurable condition that affects millions of people of all ages. If left untreated asthma attacks can be life threatening.

‘However, with appropriate treatment and thoughtful monitoring, most people will be able to successfully control their symptoms and be spared from serious harm.

‘Accurate diagnosis of asthma has been a significant problem which means that people may be wrongly diagnosed or cases might be missed in others. Our aim with this guideline is to give clarity and set out the most clinical and cost effective ways to diagnose and monitor asthma based on the best available evidence.’

DIAGNOSIS

The crux of the guideline is to move away from diagnosis made on the basis of history and clinical signs, to one made on the basis of objective tests, in particular spirometry and FeNO (fractional exhaled nitric oxide).

Currently, there is no gold standard test available to diagnose asthma and it is diagnosed principally on the basis of a thorough history taken by an experienced clinician.

A number of methods and assessments are available to determine the likelihood of asthma. These include measures of airflow obstruction, such as spirometry and peak flow, and measures of reversibility with bronchodilators, with both types of measure being widely used in current clinical practice.

This latest guideline aims to determine the most clinical and cost effective way to effectively diagnose people with asthma and determine the most effective monitoring strategy to ensure optimum asthma control.

The guideline stresses that to achieve an accurate diagnosis, objective clinical tests should be used alongside checking for signs and symptoms, and that its key recommendations on diagnosis support those made in the 2014 BTS/SIGN asthma guideline,³ ‘which also supports spirometry as the preferred initial test to assess the presence and severity of airflow obstruction.’

But the BTS/SIGN guideline’s recommendations are that initial diagnosis is made on the balance of probabilities, according to the presenting clinical features. In patients with a high probability of asthma, the first recommendation for both adults and children is to start a trial of treatment, to assess response to treatment and to reserve further testing for those with a poor response.³ (Box 1,2)

Investigations – such as spirometry – should be reserved for patients with an intermediate probability of asthma, according to the recently updated (in 2014) BTS/SIGN guideline.³

NICE says that healthcare professionals should use spirometry as the first-line investigation in adults, young people and children over the age of 5 years.¹

Further breath tests should be carried out depending on the results from spirometry and the patient’s age.

For adults, young people and children over 5 years, healthcare professionals may need to check for levels of nitric oxide, a gas which is found in larger volumes in people with asthma, using the FeNO test, and carry out a bronchodilator reversibility (BDR) test.

The treatment of under-5s should be based on professional judgement and observation until the child is old enough to take clinical tests.

Previously, we would have said that diagnosis should not be made on the basis of lung function alone – symptoms and clinical history must also be taken into account,⁶ but NICE’s new draft guideline gives far greater weight to objective tests.¹ The recommended sequence for testing is:

• Spirometry
• BDR if spirometry is positive for airways obstruction
• FeNO if BDR is negative
• Consider PEFR monitoring if FeNO is

Spirometry

Spirometry is a physiological test that measures how an individual inhales or exhales volumes of air as a function of time. Forced vital capacity (FVC) is the volume delivered during an expiration made as forcefully and completely starting from full inspiration, and forced expiratory volume in one second (FEV1) is the volume delivered in the first second of an FVC manoeuvre. A reduced ratio of FEV1 to FVC indicates airflow obstruction.

Perhaps controversially, NICE says a test for obstructive airway disease should be regarded as positive if the forced expiratory volume in 1 s/forced vital capacity (FEV1/FVC) ratio is less than 70%.¹

Importantly, spirometry testing should only be carried out by appropriately trained staff who are able to assess the correct performance of the test by the patient as well as the quality of the results. NICE accepts that spirometry is only useful if a ‘good quality spirogram is obtained’, but says that how patients might have access to high quality testing may depend on local circumstances.¹ (For a more detailed explanation, see Rachel Booker’s articles in Practice Nurse, Spirometry: getting the test right, and Spirometry: understanding the results)

Bronchodilator reversibility

Reversibility is an objective, quantifiable measure that can assist in confirming the presence of variable airflow limitation. In simple terms, the patient’s lung function is measured, they are given treatment (either a single dose of bronchodilator [B2 agonist] or a course of corticosteroid) and their lung function is measured again to see if an improvement has occurred. Whichever measure – peak expiratory flow rate (PEFR) or FEV1 – is used at baseline, should be used for the second measure. However, NICE prefers FEV1, and recommends that an increase in FEV1 ≥12% and ≥200ml above baseline FEV1 after short-acting B2 agonist constitutes a positive bronchodilator response.

Although the test is relatively simple to perform in primary care, it is not suitable for children under 5 years, and there is no direct evidence for its usefulness in those between the ages of 5 and 16.¹ The degree of reversibility may not correlate with the severity of symptoms, and patients may have poor perception of their own airflow limitation.⁴

FeNO

FeNO is not designed for use as a standalone diagnostic or management technique in the treatment of asthma, although it is accepted as a useful adjunct to existing strategies.⁵

FeNO uses a device to measure the amount of forced exhaled nitric oxide, which is produced in the lungs and present in exhaled breath. Nitric oxide has been shown to act as a vasodilator, bronchodilator, neurotransmitter and inflammatory mediator in the lungs and airways. Increased levels of nitric oxide are thought to be related to lung inflammation and asthma, and are reduced by effective treatment with inhaled corticosteroids (ICS).⁵ Results are presented in parts per billion (ppb), and a level of >35 ppb is regarded as a positive test.

NICE has approved three testing devices – NIOX NIMO, NIOX VERO and NObreath.⁶

The test is quick and non-invasive, and can be undertaken by adults and children as young as 4 years – although young children may find it difficult to expire the correct amount of breath for the optimum time needed to obtain a FeNO level.⁵

OTHER DIAGNOSTIC TESTS

The use of skin prick tests to aeroallergens, serum total and specific IgE, peripheral blood eosinophil count and exercise challenge are NOT recommended for diagnosis, although they may be useful further along the management pathway.

Direct bronchial challenge tests with histamine or methacholine in adults and young people older than 16 years should be reserved for cases where there is diagnostic uncertainty after other objective tests.

OCCUPATIONAL ASTHMA

The draft guideline gives additional emphasis to occupational asthma (OA), a form of asthma that is attributed to exposure to substances such as chemicals or dust in the workplace, and not to stimuli encountered outside the workplace. The true incidence of OA is unknown, but it is suspected that it is under-reported, and that it may affect around 1 in 10 of adults with asthma. NICE recommends that healthcare professionals should ask employed people with adult onset asthma how their symptoms are affected by work.

The guideline development group (GDG) felt that there was ‘no harm’ in asking the traditional questions, Are symptoms better on days away from work, and Are symptoms better on holiday but warned that repeated questioning could result in falsely positive responses. It is therefore suggested that the questions should be put at annual review or if there was evidence of poor asthma control, but not more frequently.

MONITORING ASTHMA CONTROL

Another area that the draft guideline covers is monitoring asthma control using symptom scores and questionnaires, and with lung function tests.

Questionnaires

Evidence suggests that both patients and clinicians tend to underestimate asthma severity and overestimate asthma control when using the simple question, ‘How is your asthma?’¹

As a result, a number of different instruments have been developed both to assess asthma-related quality of life and symptom control. But the evidence for how effective these were, in terms of reducing mortality, unscheduled healthcare use and the need for oral steroids, was poor making it difficult to recommend a specific questionnaire. However, the guideline recommends using a validated questionnaire (the Asthma Control Questionnaire or Asthma Control Test) to monitor control rather than relying on the simple question above. The GDG felt that this didn’t gather enough information to guide treatment and therefore the more formal questionnaires should be administered at annual reviews.¹

Lung function tests

Lung function does not always correlate with asthma symptoms in adults or children, but evidence of airways obstruction is a factor for poor prognosis: a low FEV1 identifies patients at risk of asthma exacerbations, independent of symptom levels, especially if FEV1 is <60% predicted.

FEV1 is considered to be the ‘gold standard’ measurement of airways obstruction due to its accurate, well standardised measurements, repeatability and reliable reference values.

PEF may provide some useful information but a normal PEF does not rule out significant airways obstruction, and the variation in normal values, particularly in healthy children, is large, reducing the value of comparison with published reference values.¹

But despite a dearth of trial evidence for the benefit of monitoring lung function versus symptom monitoring, based on current best practice, the draft guideline recommends that asthma control should be monitored at each review, either using spirometry or peak flow variability. In making the recommendation, the GDG found clinically important benefits of monitoring in terms of unscheduled GP visits, but harms in terms of increased steroid use. However, if accurate, monitoring with lung function tests could reduce medication usage and save costs.

Neither challenge testing nor FeNo should be used routinely to monitor asthma control, but FeNO can provide an option for monitoring people who are symptomatic despite using ICS, and for identifying adherence to prescribed treatment.

Adherence

The regular (daily) use of ICS is recommended for all patients other than those with mild, infrequent symptoms and low risk of exacerbation, with additional regular maintenance therapy for those failing to achieve control with standard doses of ICS alone. However, despite the proven benefits, non-adherence to treatment is common. On average patients prescribed regular ICS receive prescriptions for less than half the number of inhalers they need for regular treatment each year.¹ Non-adherence is associated with poor outcomes and increased risk in patients of all levels of asthma severity, including those with the most difficult to control asthma.

Non-adherence occurs for a variety of reasons, some intentional and some non-intentional, often relating to patient beliefs, health literacy and to clinician-patient communication. When recognised, poor adherence can be improved through various communication and management strategies, including shared decision-making and personal asthma action plans. GP computerised repeat prescribing systems allow an objective record of refill prescriptions for ICS and other medication to be accessed by clinicians, and can be assessed as part of a structured asthma review.¹

The guideline does not make any recommendation for how adherence should be monitored but says more research is needed to establish the clinical and cost effectiveness of using electronic alert systems – inhalers with built in technology to monitor use. Such devices would increase costs, but could improve outcomes. The question is whether or not the improvement would justify the extra cost.

Other interventions to monitor adherence might include using prescription and repeat data to check that inhalers are being used as prescribed, the MARS (medication adherence rating scale) questionnaire and FeNO levels – levels come down if patients are using their ICS.¹

INHALER TECHNIQUE

The selection of an appropriate inhaler device is an important part of pharmacotherapy for asthma management. With all inhalers, correct technique is essential for ensuring proper delivery of treatment. There should be proper understanding of, and training in, inhaler technique for patients, parents and/or carers. It is essential for healthcare professionals such as GPs, practice nurses, asthma nurse specialists, health visitors, school nurses, hospital doctors and nurses dealing with people with asthma-related medical problems to have an equally good understanding, so that they can provide education and support.

In line with the published NICE Quality Standard on asthma, the guideline recommends that inhaler technique should be assessed:

• After every asthma attack
• When the device is changed
• At every annual review.

The quality of the evidence for the recommendation is poor, and NICE says it is a high research priority to identify the best way of monitoring technique. Nonetheless, there is ample evidence from wider prognostic studies that poor inhaler technique predicts future risk, and the consensus was that monitoring offers clinically important benefits in lung function and quality of life even if there is no specific evidence that it reduces exacerbations or mortality.

CONCLUSION

Why do we have a new guideline from NICE?

The short answer is ‘because the Department of Health asked NICE to produce one’.¹ It doesn’t deal with treating asthma or severe or difficult to control asthma. Instead it focuses on the diagnosis of asthma and routine monitoring.

In practice, this guideline may cause more confusion than it resolves, as a number of the recommendations do not correspond with those in the widely used and respected BTS/SIGN guideline, which has been regularly updated since it was first published in 2003.

It doesn’t mention personal asthma action plans, which have been a mainstay of best practice, endorsed by BTS/SIGN and promoted by Asthma UK. Peak flow rates, which have been the bedrock of asthma management for decades have been largely sidelined in favour of more complicated, less widely available tests for both diagnosis and monitoring.

Most of all, the guideline, which is due to be published in July this year (2015), marks a significant move away from the current practice, of diagnosing asthma on the balance of probabilities. The use of objective tests, notably spirometry, may provide a more scientific approach to ensuring accurate diagnosis, but whether it will address the current problems of over- and under-diagnosis, only time will tell.

REFERENCES

1. NICE. Asthma: diagnosis and monitoring of asthma in adults, children and young people. Draft doe consultation, January 2015. http://www.nice.org.uk/guidance/gid-cgwave0640/documents/asthma-diagnosis-and-monitoring-draft-nice-guideline2

2. NICE Simple test to help diagnose and manage asthma, April 2014 http://www.nice.org.uk/news/article/simple-test-to-help-diagnose-and-manage-asthma

3. BTS/SIGN Asthma Guideline 2014. https://www.brit-thoracic.org.uk/guidelines-and-quality-standards/asthma-guideline/

4. Booth A. Reversibility testing for airflow obstruction. Practice Nurse November 2012 http://www.practicenurse.co.uk/index.php?p1=articles&p2=605

5. Stonham C. Ten-second test in the diagnosis and management of asthma. Practice Nurse, May 2014 http://www.practicenurse.co.uk/index.php?p1=articles&p2=893

6. NICE diagnostic guidance (DG12). Measuring fractional exhaled nitric oxide concentration in asthma: NIOX NIMO, NIOX VERO and NObreath, 2014. http://www.nice.org.uk/guidance/dg12