A review of reporting of participant recruitment and retention in RCTs in six major journals

Merran Toerien,Sara T Brookes,Chris Metcalfe,Tim J Peters,Zelda Tomlin,Jonathan Sterne,Isabel De Salis,Jenny L Donovan

doi:10.1186/1745-6215-10-52

Abstract

BackgroundPoor recruitment and retention of participants in randomised controlled trials (RCTs) is problematic but common. Clear and detailed reporting of participant flow is essential to assess the generalisability and comparability of RCTs. Despite improved reporting since the implementation of the CONSORT statement, important problems remain. This paper aims: (i) to update and extend previous reviews evaluating reporting of participant recruitment and retention in RCTs; (ii) to quantify the level of participation throughout RCTs.MethodsWe reviewed all reports of RCTs of health care interventions and/or processes with individual randomisation, published July–December 2004 in six major journals. Short, secondary or interim reports, and Phase I/II trials were excluded. Data recorded were: general RCT details; inclusion of flow diagram; participant flow throughout trial; reasons for non-participation/withdrawal; target sample sizes.Results133 reports were reviewed. Overall, 79% included a flow diagram, but over a third were incomplete. The majority reported the flow of participants at each stage of the trial after randomisation. However, 40% failed to report the numbers assessed for eligibility. Percentages of participants retained at each stage were high: for example, 90% of eligible individuals were randomised, and 93% of those randomised were outcome assessed. On average, trials met their sample size targets. However, there were some substantial shortfalls: for example 21% of trials reporting a sample size calculation failed to achieve adequate numbers at randomisation, and 48% at outcome assessment. Reporting of losses to follow up was variable and difficult to interpret.ConclusionThe majority of RCTs reported the flow of participants well after randomisation, although only two-thirds included a complete flow chart and there was great variability over the definition of "lost to follow up". Reporting of participant eligibility was poor, making assessments of recruitment practice and external validity difficult. Reporting of participant flow throughout RCTs could be improved by small changes to the CONSORT chart.

Highlights

Poor recruitment and retention of participants in randomised controlled trials (RCTs) is problematic but common
There is growing evidence that CONSORT has improved the quality of RCT reports [5,6,8,9], previous reviews suggest that problems remain
Literature search We searched Medline for all reports of RCTs published between July and December 2004 in six major journals: Annals of Internal Medicine, Annals of Surgery, British Medical Journal (BMJ), The Journal of the American Medical Association (JAMA), The Lancet, and The New England Journal of Medicine (NEJM)

Summary

Introduction

Poor recruitment and retention of participants in randomised controlled trials (RCTs) is problematic but common. Clear and detailed reporting of participant flow is essential to assess the generalisability and comparability of RCTs. Despite improved reporting since the implementation of the CONSORT statement, important problems remain. This paper aims: (i) to update and extend previous reviews evaluating reporting of participant recruitment and retention in RCTs; (ii) to quantify the level of participation throughout RCTs. Randomised controlled trials (RCTs) are widely acknowledged as the design of choice for evaluating the effectiveness of health care interventions. In addition to being part of the good design and conduct of trials, clear and sufficiently detailed reporting of participant flow is important in order for readers to assess the generalisability [4], relevance and comparability of trial results. Gross et al (page 3 [7]) found "sporadic and incomplete reporting of the recruitment process in many RCTs"; Devereaux et al (page 384 [5]) found "suboptimal reporting" of 11 key methodological factors even among journals supporting CONSORT; Folkes et al (page 845 [11]) found that "information pertaining to pre-randomization was often missing or incomplete"; and Mills et al (page 485 [12]) found that "even after a revision of the CONSORT statement and subscription to it by leading journals, the reporting of key methodological items continues to be poor"

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