Candy, B;
(2014)
The contribution of qualitative evidence to our understanding of the effectiveness of complex interventions.
Doctoral thesis , UCL (University College London).
Abstract
Combining qualitative and quantitative evidence may enhance understanding of how complex healthcare interventions work. How best to integrate quantitative reviews of interventions with reviews of qualitative research on patients’ views on issues relating to components of such interventions is challenging. In this thesis I used adherence to therapy as a worked example to answer: 1) How can qualitative evidence of patients’ views help understand heterogeneity of effect in complex healthcare interventions? (2) What approaches to combine different data, collected from different research disciplines, can best be applied to the mixed review evidence? I used evidence from qualitative reviews on patients’ suggestions on how to promote adherence with outputs from quantitative evidence on the effectiveness of trialled interventions promoting adherence. I compared in a table, patients’ suggestions with the content of interventions. I summarised narratively, and used analytical approaches: qualitative comparative analysis (QCA) and regression. The approaches differed in data requirements. Regression was most restricted, even when adapted for smaller datasets. QCA and regression differed in presentation: regression sought across trials the most parsimonious factors in relation to outcome; whilst QCA sought to identify multiple pathways and combinations of factors. QCA may offer understanding of most relevance in its presentation but does not provide a measure of the precision of its findings, and its weaknesses are not fully understood. The approaches generated new findings. Some concurred. The suggestions most commonly found linked to effective interventions corresponded with two distinct ways to promote adherence, one being interactive (focusing on personal risk factors) and the other more didactic (emphasising clear information). This thesis compares methods to integrate qualitative evidence on patients’ views with evidence on the effectiveness of complex interventions. It advances discussion on the value of qualitative evidence in intervention development and provides new evidence on how to promote adherence to therapy.
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