A mixed methods investigation of trial design for measuring glaucoma medication adherence

Cate, Heidi (2016) A mixed methods investigation of trial design for measuring glaucoma medication adherence. Doctoral thesis, University of East Anglia.

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Sub-optimal adherence to glaucoma therapy has negative health and financial implications. The Norwich Adherence Glaucoma Study (NAGS) adopted gold-standard methods including randomisation and objective outcome measurement to investigate an adherence intervention. Patients were randomised to standard care alone (control group) or additional glaucoma and medication related information provision using Behaviour Change Counselling. A Travalert Dosing Aid® (TDA) was used to collect 8 months of adherence data. For the 208 patients randomised, adherence was higher than expected in the control group and there was no significant difference in adherence between intervention and control.
Two qualitative studies collected user experiences from NAGS and established patient experiences of administering eye drops using the TDA. Potential NAGS experimental design errors were identified that might have inadvertently introduced changes in patient behaviour, causing bias in the observed study outcomes; a phenomenon known as a reactivity effect. Thus, the React study was designed to quantify the magnitude of reactivity effects on observed adherence behaviour, but the study required the use of a modified consent method. Focus groups informed the content of a questionnaire that was piloted using cognitive interviewing methods. The subsequent questionnaire was distributed to 400 members of the public attending an out-patient NHS hospital. From the 208 questionnaires returned, the majority of respondents felt that the proposed React study used an acceptable consent method in order to investigate reactivity effects.
Work continues with the React study to recruit the target sample size. Participants with lower measured adherence were less likely to participate and this self-selecting bias compromised estimates of the true magnitude of reactivity effects. However, the evidence collected to date confirmed the presence of reactivity effects.
This research suggests that objective measures coupled with modified consent procedures may be an appropriate methodological strategy to minimise reactivity effects in trials designed to change behaviour.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Pharmacy
Depositing User: Jackie Webb
Date Deposited: 10 Apr 2017 13:06
Last Modified: 31 Mar 2020 00:38
URI: https://ueaeprints.uea.ac.uk/id/eprint/63211


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