Non-Invasive Assessment of Airway Inflammation in Asthma: An Overview

The goals of asthma management are the accurate diagnosis and effective control of symptoms, prevention of exacerbations and the achievement and preservation of best pulmonary function. Despite improvements in asthma care patients are still misdiagnosed or undertreated. The reason for this is simple, asthma is a heterogeneous disease, but in most primary and secondary care settings only one facet, variable airflow obstruction, is addressed. The two other main aspects of asthma, airway inflammation and airway hyperresponsiveness, remain under-utilized in both diagnosis and treatment of asthma. Treatment algorithms based on airway hyperresponsiveness have been successfully used to reduce asthma exacerbations but at the expense of more corticosteroid use. Using a non-invasive marker of airway inflammation has also been shown to reduce exacerbations compared with a control group following current guidelines, but with similar steroid dose between both groups and with comparative symptom and quality of life measures. There are various non-invasive markers of airway inflammation (as opposed to bronchial biopsy and bronchoalveolar lavage). This article will concentrate on the use of the two most clinically important methods of assessing airway inflammation, namely induced sputum and exhaled nitric oxide. It will evaluate the indications, practicalities and use for each method and discuss future areas for research.