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Rapid access airway clinic

One-stop airway diagnostic service trial

We are currently planning a series of large, primary care based clinical trials but as a prelude we would like to assess the value of an inflammatory based assessment in a pilot trial of a one stop airway diagnostic service

Asthma UK has agreed to support the service which incorporates assessment of various markers of airway inflammation as well as conventional tests of airway function and will be based at Glenfield Hospital.

We are happy to assess incident (i.e. new) cases of suspected airway disease. We will feed back the results in an accessible way within 48 hours. The assessment will be different from the current physiology based classification in that it will provide information on the likely corticosteroid responsiveness of your patient’s disease as well as their diagnostic category. There will be no cost but we will ask you to report to us whether you feel that the service has been helpful.

Referrals

We are happy to receive referrals of patients newly presenting with symptoms suggesting airway disease (i.e. cough, asthma, COPD). The assessment should be done before corticosteroid treatment is started. Short acting b2-agonists can be used as necessary.

Referrals can be sent to Ian D Pavord, consultant physician and Honorary Professor of Medicine, Department of Respiratory Medicine at Glenfield Hospital

Fax: 0116 236 7768 or e-mail Prof Pavord 

Diagnosis

The diagnostic labels used to characterise common airway diseases has always been problematic.

The term “asthma” implies the presence of variable airflow obstruction. However, objective demonstration of this can be difficult. Commonly used tests are neither sensitive nor specific, particularly in patients with mild disease and normal or near normal lung function, or in those with fixed airflow obstruction.

Conversely, the term “COPD” implies largely irreversible airflow obstruction, yet clinicians may attempt to confirm the presence of “reversibility”, and having done so, label the patient as having “an asthmatic component”.

The use of specific diagnostic labels also implies a likely natural history and influences expectations regarding treatment outcomes. Although aetiological factors in the different airway diseases are clearly different, the natural history and treatment responsiveness are much less distinct.

For example, steady decline in lung function is a feature in COPD, but not exclusively so: it also occurs in a proportion of patients with asthma, and evidence suggests that the mechanisms are similar. Given this picture, the value of conventional diagnostic labelling is at best questionable and may at times be misleading.  

Treatment

Treatment with corticosteroids, usually by the inhaled route, is arguably the most important therapeutic intervention in patients with airway disease. Judicious use of these agents may result in significant improvement in symptoms and the frequency of exacerbations. However, the beneficial effects are clearly not confined to patients with objective evidence of “asthma”. Indeed, it is not possible to easily identify clinical or physiological features which predict corticosteroid responsiveness in patients with symptoms suggesting airways disease, irrespective of the final diagnosis.

One pragmatic approach in the assessment and management of airways disease is to undertake a short-term empirical “trial of steroid”. Thereafter the decision to continue long-term use of corticosteroids is usually based on the perceived short-term response. However, this is potentially flawed for a number of reasons.

Firstly, symptoms suggesting asthma are non-specific and are mimicked in conditions such as respiratory tract infection and post-viral bronchial hyper-responsiveness, and in non-pulmonary conditions such as anxiety-hyperventilation syndrome, vocal cord dysfunction, gastro-oesophageal reflux, and rhinitis with post-nasal drip. These conditions do not usually respond to corticosteroid therapy, but just as in asthma, spontaneous improvement over time may lead to the mistaken belief that corticosteroid treatment has been beneficial. The correct diagnosis is thus delayed, or inappropriately, treatment may be either continued or re-started when symptoms relapse.

Secondly, it may not be valid to draw inferences about the longer-term benefits of corticosteroid treatment (i.e. reduction in exacerbation frequency) from the outcome of a short-term trial. 

Thirdly, conventional spirometric tests of lung function may not improve with short-term treatment, confounding the interpretation of the corticosteroid trial. This is a particular issue in patients with near-normal pre-treatment test results or in those with fixed airflow obstruction.

All of these problems, together with the natural tendency of clinicians to err on the side of caution in borderline cases, increase the likelihood that patients may be committed to corticosteroid therapy inappropriately with associated cost and potential toxicity.

An alternative approach

An alternative approach is to identify the need for corticosteroid treatment in relation to the nature of the underlying airway inflammatory response (inflammometry). There is now consistent and compelling evidence from work done in Leicester that the presence of eosinophilic airway inflammation strongly predicts beneficial short and long-term responses to corticosteroid treatment. 

Moreover, it has now become feasible to assess eosinophilic airway inflammation in the clinic quickly and cheaply. The advent of exhaled nitric oxide measurements as a surrogate marker of eosinophilic airway inflammation offers the opportunity to translate what is theoretically desirable into something that is practically possible.