Retention of Patients with Schizophrenia in Complex Intervention Trials: Patterns, Issues, and Practices
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Background: Inability to retain participants in a clinical trial poses a threat to clinical research as it can lead to a number of issues ultimately affecting generalisability, validity and reliability of the study. Patients with schizophrenia have been reported as particularly difficult to engage and retain in research and psychiatric treatment. This thesis aimed to improve the current understanding of the retention of people with schizophrenia in trials evaluating complex interventions. Methods: This thesis adopted a mixed method design. Quantitative methodology was used to identify the scale of attrition and to explore potential predictors of dropout. This included a systematic review and meta-analysis and a separate meta-analysis of individual patient data. Qualitative methodology was used in two studies to explore the perspectives of both trial staff and former trial participants on the factors important for retention and effective practices and strategies. Results: The results of the systematic review and meta-analysis demonstrated the rates of dropout from studies to be higher than from experimental interventions. Dropout from interventions significantly increased as the number of intervention sessions increased. The individual patient data meta-analysis found retention to be higher at the final follow-up assessment than at the penultimate one. The effect of arm allocation almost reached statistical significance pointing to the possibility of participants in the active arm having higher odds of completing the final follow-up than those in the control arm. Two qualitative studies identified barriers and facilitators to retention related to factors related to participant, researcher, study, and wider context. Some of the identified barriers were specific to schizophrenia. Conclusion: Attrition is a phenomenon that should be anticipated by trialists and prevented with the use of multiple strategies. The extent to which dropout can be minimised depends on a number of factors associated with the participant, researcher, study, and context.
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