Strategies to improve retention in randomised trials

Area of Science:

• Clinical Trials Methodology
• Evidence Synthesis
• Health Services Research

Background:

• Loss to follow-up in randomized trials compromises study power and generalizability.
• Effective strategies to improve participant retention are crucial but often unevaluated.

Purpose of the Study:

• To quantify the impact of retention strategies on participant retention in randomized trials.
• To explore variations in strategy effectiveness based on trial type and setting.

Main Methods:

• Systematic review and meta-analysis of eligible retention trials embedded within host randomized trials.
• Inclusion of trials evaluating strategies to increase retention across all disease areas and settings.
• Data extraction on randomization methods, strategy type, comparators, and outcomes; risk ratios (RR) used for effectiveness evaluation.

Main Results:

• Monetary incentives (RR 1.18-1.25) and offers of monetary incentives significantly increased postal and electronic questionnaire response rates.
• Recorded delivery of questionnaires (RR 2.08) and a package of postal communication strategies (RR 1.43) also showed promise.
• Evidence for shorter questionnaires, disease-relevant questionnaires, non-monetary incentives, and priority post was unclear or inconclusive.

Conclusions:

• Monetary incentives are effective in improving questionnaire response rates in randomized trials.
• Few studies evaluated strategies for improving return to trial sites; further research is warranted.
• The applicability of findings depends on trial-specific factors like setting, population, and follow-up procedures.