Two-by-two factorial randomised study within a trial (SWAT) to evaluate strategies for follow-up in a randomised prevention trial

Lucy E Bradshaw, Alan A Montgomery, Hywel C Williams, Joanne R Chalmers, Rachel H Haines, Lucy E Bradshaw, Alan A Montgomery, Hywel C Williams, Joanne R Chalmers, Rachel H Haines

Abstract

Background: Failure to collect outcome data in randomised trials can result in bias and loss of statistical power. Further evaluations of strategies to increase retention are required. We assessed the effectiveness of two strategies for retention in a randomised prevention trial using a two-by-two factorial randomised study within a trial (SWAT).

Methods: Parents of babies included in the host trial were randomised to (1) short message service (SMS) notification prior to sending questionnaires at 3, 6, 12 and 18 months versus no SMS notification and (2) a £10 voucher sent with the invitation letter for the primary follow-up visit at 24 months or given at the visit. The two co-primary outcomes were collection of host trial (1) questionnaire data at interim follow-up times and (2) primary outcome at 24 months during a home/clinic visit with a research nurse.

Results: Between November 2014 and November 2016, 1394 participants were randomised: 350 to no SMS + voucher at visit, 345 to SMS + voucher at visit, 352 to no SMS + voucher before visit and 347 to SMS + voucher before visit. Overall questionnaire data was collected at interim follow-up times for 75% in both the group allocated to the prior SMS notification and the group allocated to no SMS notification (odds ratio (OR) SMS versus none 1.02, 95% CI 0.83 to 1.25). Host trial primary outcome data was collected at a visit for 557 (80%) allocated to the voucher before the visit in the invitation letter and for 566 (81%) whose parents were allocated to receive the voucher at the visit (OR before versus at visit 0.89, 95% CI 0.69 to 1.17).

Conclusion: There was no evidence of a difference in retention according to SMS notification or voucher timing. Future synthesis of SWAT results is required to be able to detect small but important incremental effects of retention strategies.

Trial registration: ISRCTN registry, ID: ISRCTN21528841. Registered on 25 July 2014. SWAT Repository Store ID 25.

Keywords: Incentive; Randomised; Retention; SWAT; Short message service.

Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Participant flow diagram
Fig. 2
Fig. 2
Kaplan-Meier curves for days to questionnaire completion according to short message service (SMS) notification allocation

References

    1. Daykin A, Clement C, Gamble C, Kearney A, Blazeby J, Clarke M, et al. ‘Recruitment, recruitment, recruitment’ – the need for more focus on retention: a qualitative study of five trials. Trials. 2018;19(1):76. doi: 10.1186/s13063-018-2467-0.
    1. Tudur Smith C, Hickey H, Clarke M, Blazeby J, Williamson P. The trials methodological research agenda: results from a priority setting exercise. Trials. 2014;15(1):32. doi: 10.1186/1745-6215-15-32.
    1. Bower P, Brueton V, Gamble C, Treweek S, Smith CT, Young B, et al. Interventions to improve recruitment and retention in clinical trials: a survey and workshop to assess current practice and future priorities. Trials. 2014;15(1):399. doi: 10.1186/1745-6215-15-399.
    1. Brueton VC, Tierney J, Stenning S, Harding S, Meredith S, Nazareth I, et al. Strategies to improve retention in randomised trials. Cochrane Database Syst Rev. 2013;12:MR000032.
    1. Treweek S, Altman DG, Bower P, Campbell M, Chalmers I, Cotton S, et al. Making randomised trials more efficient: report of the first meeting to discuss the Trial Forge platform. Trials. 2015;16(1):261. doi: 10.1186/s13063-015-0776-0.
    1. Chalmers JR, Haines RH, Mitchell EJ, Thomas KS, Brown SJ, Ridd M, et al. Effectiveness and cost-effectiveness of daily all-over-body application of emollient during the first year of life for preventing atopic eczema in high-risk children (The BEEP trial): protocol for a randomised controlled trial. Trials. 2017;18(1):343. doi: 10.1186/s13063-017-2031-3.
    1. Simpson EL, Chalmers JR, Hanifin JM, Thomas KS, Cork MJ, McLean WH, et al. Emollient enhancement of the skin barrier from birth offers effective atopic dermatitis prevention. J Allergy Clin Immunol. 2014;134(4):818–823. doi: 10.1016/j.jaci.2014.08.005.
    1. Montgomery AA, Williams HC, Chalmers JR, Bradshaw LE. SWAT 25: Two-by-two factorial randomised trial to evaluate strategies to improve follow-up in a randomised prevention trial. 2015. Available from: . Accessed 29 July 2019.
    1. Clark L, Ronaldson S, Dyson L, Hewitt C, Torgerson D, Adamson J. Electronic prompts significantly increase response rates to postal questionnaires: a randomized trial within a randomized trial and meta-analysis. J Clin Epidemiol. 2015;68(12):1446–1450. doi: 10.1016/j.jclinepi.2015.01.016.
    1. Keding A, Brabyn S, MacPherson H, Richmond SJ, Torgerson DJ. Text message reminders to improve questionnaire response rates. J Clin Epidemiol. 2016;79:90–95. doi: 10.1016/j.jclinepi.2016.05.011.
    1. Starr K, McPherson G, Forrest M, Cotton SC. SMS text pre-notification and delivery of reminder e-mails to increase response rates to postal questionnaires in the SUSPEND trial: a factorial design, randomised controlled trial. Trials. 2015;16:295. doi: 10.1186/s13063-015-0808-9.
    1. Hardy P, Bell JL, Brocklehurst P, Bick D, Briley A, Juszczak E, et al. Evaluation of the effects of an offer of a monetary incentive on the rate of questionnaire return during follow-up of a clinical trial: a randomised study within a trial. BMC Me Res Methodol. 2016;16(1):82. doi: 10.1186/s12874-016-0180-9.
    1. Young B, Bedford L, das Nair R, Gallant S, Littleford R, Robertson JFR, et al. Unconditional and conditional monetary incentives to increase response to mailed questionnaires: a randomized controlled study within a trial (SWAT). J Eval Clin Pract. 2020;26:893–902.
    1. Northern Ireland Hub for Trials Methodology Research. SWAT store 2019. Available from: . Accessed 26 July 2019.
    1. Edwards PJ, Roberts I, Clarke MJ, Diguiseppi C, Wentz R, Kwan I, et al. Methods to increase response to postal and electronic questionnaires. Cochrane Database Syst Rev. 2009;(3):Mr000008. 10.1002/14651858.MR000008.pub4.
    1. Brunsdon D, Biesty L, Brocklehurst P, Brueton V, Devane D, Elliott J, et al. What are the most important unanswered research questions in trial retention? A James Lind Alliance Priority Setting Partnership – The PRioRiTy II (Prioritising Retention in Randomised Trials) Study. Trials. 2019;20:593. doi: 10.1186/s13063-019-3687-7.
    1. National Institute for Health Research. Studies within a trial (SWAT) 2019. Available from: . Accessed 21 Oct 2019.
    1. Treweek S, Bevan S, Bower P, Briel M, Campbell M, Christie J, et al. Trial Forge Guidance 2: how to decide if a further Study Within A Trial (SWAT) is needed. Trials. 2020;21(1):33. doi: 10.1186/s13063-019-3980-5.

Source: PubMed

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