The BTS/SIGN asthma guideline incorporates the latest evidence to help GPs identify patients with occupational asthma, as Dr Hilary Pinnock explains


   

Complex guidelines, such as the British Guideline on the Management of Asthma,1 can take many months to prepare and may be out of date within weeks of publication.

To address this problem, the British Thoracic Society (BTS) and Scottish Intercollegiate Guidelines Network (SIGN) are pioneering a dynamic process that ensures that rapidly evolving aspects of the guideline are updated annually.

By publishing the asthma ‘living’ guideline on the web, some of the long delays associated with traditional publication are avoided, ensuring that advances in knowledge and understanding are incorporated into mainstream guidance as rapidly as possible.

The asthma living guideline

The 2004 update of the asthma living guideline amended the sections on medication, self-management education, and the organisation and delivery of care.In the second update, launched on 1 November 2005, the chapter on occupational asthma has been substantially rewritten, and recommendations have been amended in the chapters on inhaler devices, asthma action plans and audit.

The living guideline has been developed according to SIGN methodology.2 Evidence review groups have appraised literature published in the year to March 2004, grading their recommendations from A to D according to the strength of the evidence (Figure 1).

Although this grading system can help clinicians assess the significance of the advice contained in guidelines, it is important to appreciate that not all questions are best answered by the randomised controlled trials needed for grade A recommendations.' Lower' grades of evidence may be of considerable clinical relevance.

Members of the BTS/SIGN occupational asthma sub-group worked with the British Occupational Health Research Foundation to develop the recently published guideline on occupational asthma.3 A distillation of their comprehensive review, highlighting the key recommendations, is included in Chapter 8 of the asthma living guideline.

Figure 1: Key to evidence statements and grades of recommendation

Occupational asthma

Perhaps the most important message for primary care clinicians is the need to consider occupational causes for asthma that starts, or recurs, in adult life. There are several hundred causative agents, but the most frequently reported include isocyanates, flour and grain dust, colophony and fluxes, latex, animals, aldehydes and wood dust.

The workers at highest risk therefore are paint sprayers, bakers and pastry makers, nurses, chemical workers, animal handlers, welders, food processing workers and those who work with timber.

Surveys suggest that up to 15% of cases of adult onset asthma may have an occupational cause for their symptoms,4 yet routine identification is rare – indeed, many primary care clinicians will struggle to remember when they last diagnosed occupational asthma.

The best screening question is:"Are your symptoms better on days away from work?” (Box 1). Asking about symptoms that are worse at work is less sensitive as this question will overlook patients who deteriorate some hours after exposure.

Although these questions are not specific to work-related asthma (for example, a patient who is allergic to the family's pet cat may improve on holiday), positive answers should trigger a careful occupational history. Objective tests will be needed to confirm or refute the diagnosis.

In patients with adult onset, or reappearance of childhood asthma, clinicians should be suspicious that there may be an occupational cause (Grade B)

.

Peak flow measurement
Although specific bronchial provocation testing is considered the gold standard diagnostic test, serial peak flow measurements offer good specificity and sensitivity and can be carried out in general practice.5

Record forms available from www.occupationalasthma.com include clear instructions for the patient on how and when to take peak flow readings:

  • Please measure your peak flow every two hours from waking to sleeping, making the first reading as soon as you wake up.
  • Write down the hours that you actually work each day. If you did not work at all put a zero (0).

A booklet for clinicians, also available on this website,6 gives practical advice on recording and interpreting the results of the peak flow charting.

However, the patient will need to be referred to a respiratory physician for confirmation of the diagnosis.

Objective diagnosis of occupational asthma should be made using serial peak flow measurements, with at least four readings per day (Grade D).

Removing the worker from exposure
The cornerstone of management is to remove the worker from exposure, preferably within 12 months of sensitisation because the prognosis is worse after longer periods of exposure.

Ideally, the worker should be able to continue in worthwhile employment but, unfortunately, this is not always possible. GPs and asthma nurses who counsel patients with work-related symptoms need to be aware that a third of workers will be unemployed following a diagnosis of occupational asthma.7,8

Relocation away from exposure should occur as soon as diagnosis is confirmed, and ideally within 12 months of the first work-related symptoms of asthma (Grade D).

Box 1: Key recommendations of the 2005 update of the asthma living guideline

Occupational asthma

  • In patients with adult onset, or reappearance of childhood asthma, clinicians should be suspicious that there may be an occupational cause.
  • Adults with airflow obstruction should be asked:
    • Are you better on days away from work?
    • Are you better on holiday?
    Those with positive answers should be investigated for occupational asthma
  • Objective diagnosis of occupational asthma should be made using serial peak flow measurements, with at least four readings per day
  • Relocation away from exposure should occur as soon as diagnosis is confirmed, and ideally within 12 months of the first work-related symptoms of asthma

Inhaler devices

  • Children and adults with mild and moderate exacerbations of asthma should be treated by pMDI and spacer with doses titrated according to clinical response

Asthma action plans

  • Patients with asthma should be offered self-management education that should focus on individual needs, and be reinforced by a written action plan

Inhaler devices

The 2005 update emphasises and extends the recommendation that mild and moderate exacerbations of asthma should be treated with multiple actuations of bronchodilator from a pressurised metered dose inhaler and a spacer device (pMDI + spacer).

Previously cited systematic reviews showed that using a pMDI and spacer is as effective as a nebuliser in older children and adults. Evidence is now included that extends this recommendation to children.9 In lifethreatening asthma, however, there are no data on which to make recommendations.

This recommendation has implications for clinicians in primary care, who treat most acute exacerbations. 10,11 The trials have included a broad range of spacer devices and the advice therefore holds true for both large and small volume spacers.

There are some important practical points to note:

  • The spacer should be compatible with the pMDI being used (refer to the manufacturer’s instructions)
  • The drug should be administered by repeated single actuations of the metered dose inhaler into the spacer, each followed by inhalation.‘ Five puffs at a time’may seem quicker, but it is less effective
  • There should be minimal delay between pMDI actuation and inhalation
  • Tidal breathing is as effective as single breaths
  • The dose given should be titrated according to the response.

Children and adults with mild and moderate exacerbations of asthma should be treated by pMDI + spacer with doses titrated according to clinical response (Grades A in adults, A in children 5-12 years, B in children under 5 years).

Figure 2: First page of the two-page asthma action plan, available from Asthma UK
Figure 3: Second page of the Asthma UK action plan

Asthma action plans

The importance of asthma action plans (Figures 2 and 3) has been a consistent message, reiterated in all the guidelines published since 1990. The additional evidence cited in the 2005 update is of particular interest to primary care as it supports the assertion that patients with milder asthma will also benefit from an action plan.12

The nGMS contract has focused attention on the importance of regular review.13

The updated chapter on audit emphasises the importance of including self-management education in routine reviews, and suggests that the provision of personal asthma action plans is an appropriate criterion for audit.

New self-management educational materials have been produced by Asthma UK under the umbrella title Be in Control. They include asthma action plans suitable for individuals with milder asthma as well as those with frequent exacerbations and hospitalisations, and are accompanied by advice for the health professional on how to complete them.

The action plans can be downloaded from the Asthma UK website: www.asthma.org.uk.

Patients with asthma should be offered self-management education that should focus on individual needs, and be reinforced by a written action plan (Grade A).

Conclusion

The 2005 update of the BTS/SIGN asthma guideline includes some useful recommendations for primary care. It highlights the need to consider occupational causes for asthma symptoms in adults, recommends the use of a pMDI and spacer for the treatment of all but the most severe asthma attacks, and reiterates the importance of providing self-management education.

Adoption of these recommendations should improve care for people with asthma.

Websites

The updated chapters may be downloaded from the BTS and SIGN websites (www.brit-thoracic.org.uk and www.sign.ac.uk).

Changes to the original text are in blue and indicated with arrows labelled '2005', adding to the 2004 updates which appear in red. Further updates are planned for 2006, with a major revision scheduled for 2007.

References

  1. The British Thoracic Society/Scottish Intercollegiate Guidelines Network. British Guideline on the Management of Asthma. Thorax 2003; 58(S1): i1-94.
  2. Scottish Intercollegiate Guidelines Network. SIGN 50. A guideline developer’s handbook. Edinburgh: SIGN, 2001.
  3. Newman Taylor AJ, Nicholson PJ, eds. Guidelines for the prevention, identification and management of occupational asthma: Evidence review and recommendations. London: British Occupational Health Research Foundation, 2004. www.bohrf.org.uk/ downloads/asthevre.pdf
  4. Balmes J, Becklake M, Blanc P et al; Environmental and Occupational Health Assembly, American Thoracic Society. American Thoracic Society Statement: Occupational contribution to the burden of airway disease.Am J Respir Crit Care Med 2003; 167: 787-97.
  5. Gannon PF, Newton DT, Belcher J et al. Development of OASYS-2: a system for the analysis of serial measurement of peak expiratory flow in workers with suspected occupational asthma. Thorax 1996; 51: 484-9.
  6. Burge S. Occupational asthma. Practical Issues in Asthma Management 2000; 24: 1-10. www.occupationalasthma.com/occupational asthma/overview.pdf
  7. Cannon J, Cullinan P, Newman Taylor A et al. Consequences of occupational asthma. Br Med J 1995; 311: 602-3.
  8. Ameille J, Pairon JC, Bayeux MC et al. Consequences of occupational asthma on employment and financial status: a follow-up study. Eur Respir J 1997; 10: 55-8.
  9. Delgado A, Chou KJ, Silver EJ, Crain EF. Nebulizers vs metered-dose inhalers with spacers for bronchodilator therapy to treat wheezing in children aged 2 to 24 months in a pediatric emergency department. Arch Pediatr Adolesc Med 2003; 157: 76-80.
  10. Neville RG, Clark RC, Hoskins G, Smith B. National asthma attack audit 1991-2. General Practitioners in Asthma Group. Br Med J 1993; 306: 559-62.
  11. Pinnock H, Johnson A, Young P, Martin N. Are doctors still failing to assess and treat asthma attacks? An audit of the management of acute attacks in a health district. Respir Med 1999; 93: 397-401.
  12. Thoonen BP,Schermer TR,Van Den Boom G et al. Self-management of asthma in general practice, asthma control and quality of life: a randomised controlled trial. Thorax 2003; 58: 30-6.
  13. Investing in general practice. The New General Medical Services Contract. www.bma.org.uk.

Guidelines in Practice, November 2005, Volume 8(11)
© 2005 MGP Ltd
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