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Research Article
Revised

An embedded randomised controlled retention trial of personalised text messages compared to non-personalised text messages in an orthopaedic setting

[version 2; peer review: 2 approved]
PUBLISHED 15 Sep 2021
Author details Author details
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This article is included in the Studies Within A Trial (SWAT) collection.

Abstract

Background: Several studies have investigated whether personalising trial documentation can aid recruitment and retention. We did a ‘study within a trial’ (SWAT) evaluating the effectiveness of a personalised text message compared to a non-personalised text message, on the retention rate in a large orthopaedic trial.
Methods: The SWAT was embedded in the Knee Replacement Bandaging Study (KReBS) trial. The primary outcome was the proportion of 12-month questionnaires returned. Secondary outcomes were the proportion of questionnaires completed and time to questionnaire return. Binary data were analysed using logistic regression and time to return using Cox proportional hazards regression.  Odds ratios (OR) and hazard ratios (HR) are presented, with associated 95% confidence intervals (CI) and p-values.
Results: In total, 1465 participants were included in the SWAT. In the personalised group, 644/723 (89.1%) of participants returned a questionnaire, compared to 654/742 (88.1%) in the non-personalised group. The absolute difference in return rate was 0.9% (95% CI: -2.3% to 4.2%; p=0.57). There was no evidence of a difference between the groups in the likelihood of returning a questionnaire (OR 1.09; 95% CI: 0.79 to 1.51; p=0.61), the likelihood of returning a complete questionnaire (OR 1.11; 95% CI: 0.82 to 1.51; p=0.50) nor in time to return (HR 1.05; 95% CI: 0.94 to 1.17; p=0.40).
Conclusion: This SWAT adds to the growing evidence base for whether personalised text messages are effective.

Registration: ISRCTN87127065 (20/02/2017); SWAT 35 (01/12/2015)

Keywords

SWAT, Study Within A Trial, attrition, SMS, text messages

Revised Amendments from Version 1

We have added additional detail to the article in response to the issues raised by the reviewer. We have outlined how the validity of the phone numbers was checked at two different stages, and also provided detail on the pre-planned retention strategies.

We have also made a minor amendment to the results in light of a duplicate randomisation that was found in the host trial, which means that 2334 rather than 2335 participants were randomised to the host trial. This duplicate randomisation was not randomised to the SWAT and therefore has no other impact on the results. We have updated the figure to take this change into account.

See the authors' detailed response to the review by Michelle E Kho

Introduction

Clinical trialists have identified the recruitment and retention of participants as key issues for randomised controlled trials (RCT)1,2.

Several studies have investigated whether personalising trial documentation can aid recruitment and retention3,4. Recently, Cochrane et al. looked at the effect of personalised text messages compared to standard text messages in improving retention rates5. This study was carried out in response to a number of embedded trials evaluating the effectiveness of SMS messages in improving retention rates611, alongside a study suggesting personalised messages increased the payment of delinquent fines12.

To further add to the evidence on the effectiveness of personalised text messages, we did a ‘study within a trial’ (SWAT) evaluating the effectiveness of a personalised text message compared to a non-personalised text message on postal questionnaire response rates in a large orthopaedic trial.

Methods

Design

This paper details the methods and results of a SWAT embedded within the prospectively registered Knee Replacement Bandaging Study (KReBS) RCT (ISRCTN87127065, registered on 20 February 2017). KReBS evaluated the effectiveness of a two-layer compression bandage compared with a standard wool and crepe bandage applied post-operatively on patient-reported outcomes in total knee replacement patients13.

Participants

The SWAT was conducted in 26 NHS hospital trust sites and was implemented at the start of the study. All KReBS participants were eligible for this SWAT provided they had opted in to receiving SMS messages and were not deceased or withdrawn from follow-up before being due to be sent their 12-month postal questionnaire.

Intervention

Participants in the SWAT were sent either a personalised or non-personalised text message (Table 1) four days after their 12-month questionnaire was sent.

Table 1. Description of the contents of the personalised and non-personalised text messages.

Text message typeText message content
Personalised“KReBS Trial: [Title] [Surname] you should have received a questionnaire in the post by now.
Your answers are important; so please help by returning it as soon as you can. Thanks”
Non-personalised“KReBS Trial: You should have received a questionnaire in the post by now. Your answers
are important; so please help by returning it as soon as you can. Thanks”

KReBS - Knee Replacement Bandaging Study

The validity of the phone number given by participants was checked at two different stages. At the first stage, after randomisation, invalid numbers not beginning with “07”, which are the first two digits of all UK mobile phone numbers were removed from the database, participants providing numbers such as these were not sent a text message. The second stage occurred at the point of the text messages being sent out. Some participants provided phone numbers that began with “07”, but were actually invalid and therefore not picked up at the first stage. An attempt to send a text message to the phone number would have resulted in a failure in the message being delivered.

All SWAT participants received pre-planned retention strategies within KReBS. This consisted of a reminder letter and additional copy of the questionnaire if the participant had not returned a completed copy 4 weeks after sending out the original copy. If there was still no response following the postal reminder, participants were contacted by telephone to obtain the patient-reported outcomes.

Outcomes

The primary outcome was the proportion of participants who returned a 12-month questionnaire. Secondary outcomes were the proportion of participants who completed the questionnaire and time to questionnaire return. A questionnaire was considered complete if the participant had answered 11 or more questions of the 12-item host trial primary outcome, the Oxford Knee Score14.

Sample size

Since this was an embedded trial, the sample size was determined by the number of participants in the main KReBS trial13, which aimed to recruit 2600 participants.

Randomisation

Participants were randomised into the SWAT using simple randomisation in a 1:1 allocation ratio. The allocation schedule was generated by a researcher at the York Trials Unit not involved in the recruitment or follow-up of participants.

Blinding

Participants were not informed of their explicit participation in the SWAT, but due to the nature of the intervention could not be blinded to whether the text was personalised or non-personalised. Similarly, it was not possible to blind research staff to SWAT allocation.

Approvals

The SWAT was approved by the Research Ethics Committee North East – Newcastle and North Tyneside on 13/04/2018 (REC Number 16/NE/0400; Amendment Number 16/NE/0400/AM14). As the SWAT was deemed to be low risk, explicit informed consent was not obtained for participation.

Statistical analysis

Analyses were carried out using Stata v16.015. A diagram detailing the flow of participants through the SWAT is provided, and baseline characteristics are presented by SWAT allocation. Outcomes are summarised descriptively. Statistical tests were two-sided using a 5% significance level, and were done on an intention to treat basis. All analyses (except the calculation of the absolute difference in return rate which was estimated using the two-sample test of proportions) used mixed effects regression, adjusting for SWAT allocation and host trial allocation as fixed effects and trial site as a random effect. Relevant parameter estimates are presented with associated 95% confidence intervals and p-values.

The proportion of participants who returned a 12-month questionnaire, and proportion complete, was analysed using logistic regression. A second SWAT evaluating receipt of a pen on response rates was also embedded in KReBS at 12 months16. In a sensitivity analysis, we additionally adjusted the primary model for pen SWAT allocation.

Time to questionnaire return was analysed using a Cox proportional hazards shared frailty model. Participants who did not return a questionnaire were censored at 90 days.

Results

In total, 2334 participants were recruited into the KReBS trial and 1470 were randomised to the SWAT (Figure 1). The average age was 66.8 years and 54.0% were female (Table 217). Five participants died or withdrew following randomisation and as a result 723 participants in the personalised group, and 742 in the non-personalised group, were sent a 12-month questionnaire and were included in the analysis. Of these, 680 (94.1%) of the 723 participants in the personalised group, and 701 (94.5%) of the 742 in the non-personalised group, were sent a text.

d601d94f-d398-4e66-9d45-65cf8c8a1d12_figure1.gif

Figure 1. Study flow diagram.

Table 2. Baseline characteristics of the study within a trial (SWAT) participants.

Personalised
(n=726)
Non-personalised
(n=744)
Total
(n=1470)
Gender, n (%)
    Male
    Female
    Missing

335 (46.1)
391 (53.9)
0 (0)

340 (45.7)
403 (54.2)
1 (0.1)

675 (45.9)
794 (54.0)
1 (0.1)
Age
    n (%)
    Mean (SD)
    Median (IQR)

726 (100)
66.9 (8.5)
67.2 (60.7, 72.9)

743 (99.9)
66.8 (8.5)
67.0 (60.8, 72.4)

1469 (99.9)
66.8 (8.5)
67.1 (60.8, 72.7)
Oxford Knee Score
    n (%)
    Mean (SD)
    Median (IQR)

576 (79.3)
20.4 (8.0)
20 (14, 26)

582 (78.2)
20.5 (8.0)
20 (15, 26)

1158 (78.8)
20.4 (8.0)
20 (15, 26)

In the personalised group, 644/723 (89.1%) participants returned a questionnaire, compared to 654/742 (88.1%) in the non-personalised group (Table 317). The absolute difference in return rate was 0.9% (95% CI: -2.3% to 4.2%; p=0.57). There was no evidence of a difference between the groups in the likelihood of returning a questionnaire (OR 1.09; 95% CI: 0.79 to 1.51; p=0.61), the likelihood of returning a complete questionnaire (OR 1.11; 95% CI: 0.82 to 1.51; p=0.50) nor in time to return (HR 1.05; 95% CI: 0.94 to 1.17; p=0.40). In total, 1465 participants were also randomised to the pen SWAT. When the primary model was repeated with the addition of pen SWAT allocation, the results remained the same.

Table 3. Descriptive summaries of primary and secondary outcomes.

Personalised
(n=723)
Non-personalised
(n=742)
Total
(n=1465)
Returned questionnaire, n (%)
    Yes
    No

644 (89.1)
79 (10.9)

654 (88.1)
88 (11.9)

1298 (88.6)
167 (11.4)
Completed questionnaire, n (%)
    Yes
    No

634 (87.7)
89 (12.3)

641 (86.4)
101 (13.6)

1275 (87.0)
190 (13.0)
Time to return, days
    n (%)
    Mean (SD)
    Median (IQR)

644 (100)
15.9 (15.0)
10 (8, 16)

654 (100)
17.0 (20.4)
10 (8, 16)

1298 (100)
16.5 (17.9)
10 (8, 16)

Discussion

This embedded trial found little evidence to suggest personalised text messages are more effective than non-personalised text messages in encouraging return and completion of questionnaires. The trial did not find evidence of a statistically significant difference between groups in any of the outcomes, although effect size estimates favoured the personalised group. On the other hand, while Cochrane and colleagues also did not find evidence of a statistically significant difference between groups, estimates of effect mostly favoured the non-personalised group5.

The SWAT had a large sample size, which means the results can be generalised to other orthopaedic studies. However, completion rate was calculated as a proportion of all SWAT participants rather than all SWAT participants who returned a questionnaire, and as a result questionnaire completion was highly correlated with questionnaire return. In addition, some participants included in the analysis did not receive a text message.

Conclusion

This SWAT adds to the growing evidence base for whether personalised trial documentation, in particular text messages, are effective.

Data availability

Underlying data

Open Science Framework: Underlying data and CONSORT diagram for an embedded randomised controlled retention trial of personalised text messages compared to non-personalised text messages in an orthopaedic setting. https://doi.org/10.17605/OSF.IO/KHJ8E17

This project contains the following underlying data:

  • - KReBS_Text_SWAT_Clean.sas (Study data in SAS compatible format)

  • - KReBS_Text_SWAT_Clean.csv (Study data in .csv format)

  • - KReBS_Text_SWAT_Clean_Key.xlsx (Key for datasets)

Reporting guidelines

Open Science Framework: CONSORT checklist for ‘An embedded randomised controlled retention trial of personalised text messages compared to non-personalised text messages in an orthopaedic setting’ https://doi.org/10.17605/OSF.IO/KHJ8E17

Data are available under the terms of the Creative Commons Zero "No rights reserved" data waiver (CC0 1.0 Public domain dedication).

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Mitchell AS, Cook L, Dean A et al. An embedded randomised controlled retention trial of personalised text messages compared to non-personalised text messages in an orthopaedic setting [version 2; peer review: 2 approved]. F1000Research 2021, 9:591 (https://doi.org/10.12688/f1000research.24244.2)
NOTE: If applicable, it is important to ensure the information in square brackets after the title is included in all citations of this article.
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Open Peer Review

Current Reviewer Status: ?
Key to Reviewer Statuses VIEW
ApprovedThe paper is scientifically sound in its current form and only minor, if any, improvements are suggested
Approved with reservations A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit.
Not approvedFundamental flaws in the paper seriously undermine the findings and conclusions
Version 2
VERSION 2
PUBLISHED 15 Sep 2021
Revised
Views
8
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Reviewer Report 10 May 2022
David J Keene, University of Oxford, Oxford, UK 
Approved
VIEWS 8
Thank you for the invitation to review this interesting SWAT report. I note the other peer reviewers comments and responses. Overall this concise summary documents a well-designed and conducted SWAT. The authors are to be commended given the delivery was ... Continue reading
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HOW TO CITE THIS REPORT
Keene DJ. Reviewer Report For: An embedded randomised controlled retention trial of personalised text messages compared to non-personalised text messages in an orthopaedic setting [version 2; peer review: 2 approved]. F1000Research 2021, 9:591 (https://doi.org/10.5256/f1000research.77319.r128647)
NOTE: it is important to ensure the information in square brackets after the title is included in all citations of this article.
Version 1
VERSION 1
PUBLISHED 11 Jun 2020
Views
34
Cite
Reviewer Report 03 Jul 2020
Michelle E Kho, School of Rehabilitation Science, McMaster University, Hamilton, ON, Canada 
Approved
VIEWS 34
Mitchell et al. elegantly describe a SWAT of personalized vs. non-personalized reminder text messages embedded in a randomized orthopaedic trial. The primary outcome was questionnaire return at 12 months, and the secondary outcomes were proportion of completed questionnaires, and time ... Continue reading
CITE
CITE
HOW TO CITE THIS REPORT
Kho ME. Reviewer Report For: An embedded randomised controlled retention trial of personalised text messages compared to non-personalised text messages in an orthopaedic setting [version 2; peer review: 2 approved]. F1000Research 2021, 9:591 (https://doi.org/10.5256/f1000research.26744.r64613)
NOTE: it is important to ensure the information in square brackets after the title is included in all citations of this article.
  • Author Response 15 Sep 2021
    Alex Mitchell, Department of Health Sciences, University of York, UK, York, Y010 5DD, UK
    15 Sep 2021
    Author Response
    We thank the reviewer for her positive feedback and constructive comments, to which we have responded below. In addition to responding to the comments, we have made a minor amendment ... Continue reading
COMMENTS ON THIS REPORT
  • Author Response 15 Sep 2021
    Alex Mitchell, Department of Health Sciences, University of York, UK, York, Y010 5DD, UK
    15 Sep 2021
    Author Response
    We thank the reviewer for her positive feedback and constructive comments, to which we have responded below. In addition to responding to the comments, we have made a minor amendment ... Continue reading

Comments on this article Comments (0)

Version 2
VERSION 2 PUBLISHED 11 Jun 2020
Comment
Alongside their report, reviewers assign a status to the article:
Approved - the paper is scientifically sound in its current form and only minor, if any, improvements are suggested
Approved with reservations - A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit.
Not approved - fundamental flaws in the paper seriously undermine the findings and conclusions
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