The role of beliefs in predicting adherence to nebulised therapy in adolescents with cystic fibrosis

Introduction: Sub-optimal treatment adherence in Cystic Fibrosis (CF) is commonplace, and is known to deteriorate in adolescence, increasing risk of early morbidity and mortality. Although, in other chronic conditions, research focusing on psychological models of beliefs, and in particular the Necessity-Concerns Framework, has proved promising to understand this problem, comparatively little exists within CF. Importantly, the devices used to deliver nebulised treatments in CF provide objective recording of dose consumption, offering a singular opportunity to overcome the largest barrier in adherence research - subjective adherence measurement. However, the existing studies in CF which have examined this model in these treatments, have either relied on subjective measurement of adherence, and/or inadequately adapted the measure used to assess these beliefs. Method: This thesis was completed in two parts. Study one developed a systematic process for adapting the BMQ-S into two versions, to separately capture necessity and concern beliefs of patients and their parents which may influence adherence behaviour to both categories of nebulised medications. This process included a modified two-round Delphi survey which elicited feedback from an expert panel on the value and clarity of the adapted questionnaires. Study two examined the relationship between beliefs elicited by the measures, and objectively-recorded adherence behaviour, to assess their relative utility in predicting adherence behaviour to nebulised treatments, from both patients’, and their parents’, beliefs. Results: In study one, consensus on the value of items in both questionnaires was positive, but more variable for clarity, causing two original items to be removed, eight revised, and three created in each of the adapted measures. Study two found no significant relationships between patients’ or parents’ necessity and concern beliefs, and objectively-recorded adherence behaviour, in either medication category, in the original or adapted measures. Although analyses were underpowered by inadequate sample sizes, findings suggest that the Necessity-Concerns Framework may relate to adherence differently between nebulised medication categories and respondents, and, most importantly, that the original measure may be superior in capturing these relations. Discussion: Although the results of this research are provisional, the novelty of design in both studies highlights several important considerations for future research, including the importance of assessing the psychometric properties of adapted belief measures, rather than assuming that refined versions will necessarily be superior to original versions. They also highlight the importance of considering parents beliefs when trying to understand adherence behaviour in adolescent populations.