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The randomization process involves assigning study participants randomly to experimental or control groups based on their probability of being equally assigned. Randomization is meant to eliminate selection bias and balance known and unknown confounding factors so that the control group is similar to the treatment group as much as possible. A computer program and a random number generator can be used to assign participants to groups in a way that minimizes bias.
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Randomised trials conducted using cohorts: a scoping review.

Beverley Jane Nickolls¹, Clare Relton², Lars Hemkens^3,4,5,6

¹Centre for Evaluation and Methods, Wolfson Institute of Population Health, Queen Mary University of London, London, UK b.nickolls@qmul.ac.uk.

|March 8, 2024

Summary

Cohort studies are increasingly used as data infrastructures for randomized controlled trials (RCTs), enhancing participant recruitment and outcome assessment. This growing trend necessitates standardized guidance for designing and reporting such integrated research.

Keywords:

Clinical Trial Decision Making Patient Participation Patient-Centered Care Randomized Controlled Trial STATISTICS & RESEARCH METHODS

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Area of Science:

Clinical Research Methodology
Epidemiology
Biostatistics

Background:

Cohort studies provide longitudinal data valuable for various research aims.
Randomized controlled trials (RCTs) are increasingly leveraging cohort studies as data infrastructures.
This integration aids in participant identification, recruitment, and outcome assessment for RCTs.

Purpose of the Study:

To examine the extent, range, and nature of research utilizing cohorts for RCTs.
To describe the diverse definitions and conceptual boundaries of RCTs that incorporate cohort data.
To identify trends and challenges in the use of cohort studies within RCT frameworks.

Main Methods:

A scoping review methodology was employed.
Searches were conducted in MEDLINE and EBM Reviews-Cochrane Methodology Registry in January 2021.
Eligibility criteria included reports from January 2007 to December 2021 concerning cohorts for RCTs, RCTs using cohorts, or methodological studies.

Main Results:

175 full-text articles were assessed, identifying 61 protocols, 9 cohort descriptions, 39 RCTs using cohorts, and 34 methodological papers.
The use of cohorts in RCTs is expanding across diverse fields like population health, oncology, and mental health.
Reported benefits include more efficient recruitment, representative samples, and reduced disappointment bias and crossovers.

Conclusions:

The integration of cohort studies within RCTs is a growing and evolving research approach.
Inconsistencies in terminology and concepts highlight a need for clear definitions.
Development of guidance for designing and reporting RCTs conducted using cohorts is essential.