The Clinical Assessment of Asthma, an Investigation into its Strengths and Imprecisions

Asthma is a chronic inflammatory disease characterised by airflow obstruction and reversibility. The mainstay of treatment is inhaled corticosteroids, however, despite their success some patients remain symptomatic and continue to have exacerbations. They are considered to have severe asthma, which is further divided into refractory or difficult-to-treat asthma. Difficult-to-treat asthma is often due to poor inhaler adherence/technique, or the co-existence of a comorbid condition. In cases of refractory asthma, biologic therapy is often required, however, accurate assessment is important as these are a limited resource in many healthcare systems due to their cost. Many tools used in asthma assessment were validated against uncomplicated asthma, not assessing for the impact of comorbid disease. Furthermore, there is little guidance available on how to approach the assessment of inhaler adherence or the impact of comorbid diseases on asthma symptom burden. This thesis aims to investigate the imprecisions of the clinical assessment of asthma and how this leads to the overestimation of severity and subsequent overtreatment of asthma.

First, I analysed the peak flow from a cohort of patients with and without asthma assess if diurnal variation could identify cases of uncontrolled asthma. I then analysed data from a randomised control trial to assess if incorporating objectively recorded adherence and lung function into clinical decision making improves clinical outcomes. I performed further analysis on this data to assess the effect of comorbidities on asthma control. I then examined the relationship between the BMI and asthma control questionnaires in the literature, to examine how the confounding effects of BMI may be impacting outcomes of trials. Next, I investigated patient-selected treatment goals of asthma, with the aim of identifying factors that facilitate/limit the achievement of these goals.

Finally, I discuss the implications of the results of this thesis and propose a model to incorporate the findings of this thesis into the clinical assessment of asthma.