Identifying asthma and differentiating this group of diseases from COPD on the basis of airflow obstruction and its degree of reversibility is likely to be unreliable in many older patients who present with wheeze and airflow obstruction. Irreversible airflow obstruction may be seen in asthma, particularly in those who are elderly. The prevalence and risk factors of irreversible airflow obstruction are poorly described. A proportion of airflow obstruction in COPD is reversible in many patients and the reversible component is principally in relation to bronchodilator use. Corticosteroid reversibility that is found in a small proportion of patients with COPD appears to correlate with features of asthma such as airway eosinophilia. Particularly with the development of drugs that are more specific to asthma or COPD, there is a great need for more diagnostically reliable investigations that are noninvasive and simple to perform. Induced sputum and measurements of exhaled air have the advantage that they can be applied in an older population and may be possible to offer in secondary care as an open access diagnostic support service to primary care where the bulk of patients are. The value of these investigations in clinical practice is currently being researched.
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