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Does a monetary incentive improve the response to a postal questionnaire in a randomised controlled trial? The MINT incentive study.

Gates S, Williams MA, Withers E, Williamson E, Mt-Isa S, Lamb SE - Trials (2009)

Bottom Line: Sending a monetary incentive with postal questionnaires has been found to improve the proportion of responders, in research in non-healthcare settings.The proportion of questionnaires returned (RR 1.10 (95% CI 1.05, 1.16)) and the proportion returned without chasing (RR 1.14 (95% CI 1.05, 1.24) were higher in the incentive group, and the overall non-response rate was lower (RR 0.68 (95% CI 0.53, 0.87)).Analysis of costs suggested a cost of 67.29 POUNDS per additional questionnaire returned.

View Article: PubMed Central - HTML - PubMed

Affiliation: Warwick Medical School Clinical Trials Unit, University of Warwick, Coventry, UK. s.gates@warwick.ac.uk

ABSTRACT

Background: Sending a monetary incentive with postal questionnaires has been found to improve the proportion of responders, in research in non-healthcare settings. However, there is little research on use of incentives to improve follow-up rates in clinical trials, and existing studies are inconclusive. We conducted a randomised trial among participants in the Managing Injuries of the Neck Trial (MINT) to investigate the effects on the proportion of questionnaires returned and overall non-response of sending a 5 pounds gift voucher with a follow-up questionnaire.

Methods: Participants in MINT were randomised to receive either: (a) a 5 POUNDSgift voucher (incentive group) or (b) no gift voucher (no incentive group), with their 4 month or 8 month follow-up questionnaire. We recorded, for each group, the number of questionnaires returned, the number returned without any chasing from the study office, the overall number of non-responders (after all chasing efforts by the study office), and the costs of following up each group.

Results: 2144 participants were randomised, 1070 to the incentive group and 1074 to the no incentive group. The proportion of questionnaires returned (RR 1.10 (95% CI 1.05, 1.16)) and the proportion returned without chasing (RR 1.14 (95% CI 1.05, 1.24) were higher in the incentive group, and the overall non-response rate was lower (RR 0.68 (95% CI 0.53, 0.87)). Adjustment for injury severity and hospital of recruitment to MINT made no difference to these results, and there were no differences in results between the 4-month and 8-month follow up questionnaires. Analysis of costs suggested a cost of 67.29 POUNDS per additional questionnaire returned.

Conclusion: Monetary incentives may be an effective way to increase the proportion of postal questionnaires returned and minimise loss to follow-up in clinical trials.

Trial registration number: ISRCTN61305297.

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Related in: MedlinePlus

CONSORT diagram.
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Figure 1: CONSORT diagram.

Mentions: The total number of participants in the incentive study was 2,144 (Figure 1). Of these, 1,194 were randomised at the 4 month time point, and 950 at 8 months. Balance between the study arms in patient characteristics and centre of recruitment to MINT was good. There were only small imbalances in centre of recruitment and in severity of injury, measured by the WAD (Whiplash Associated Disorder) grading system[8].


Does a monetary incentive improve the response to a postal questionnaire in a randomised controlled trial? The MINT incentive study.

Gates S, Williams MA, Withers E, Williamson E, Mt-Isa S, Lamb SE - Trials (2009)

CONSORT diagram.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2710321&req=5

Figure 1: CONSORT diagram.
Mentions: The total number of participants in the incentive study was 2,144 (Figure 1). Of these, 1,194 were randomised at the 4 month time point, and 950 at 8 months. Balance between the study arms in patient characteristics and centre of recruitment to MINT was good. There were only small imbalances in centre of recruitment and in severity of injury, measured by the WAD (Whiplash Associated Disorder) grading system[8].

Bottom Line: Sending a monetary incentive with postal questionnaires has been found to improve the proportion of responders, in research in non-healthcare settings.The proportion of questionnaires returned (RR 1.10 (95% CI 1.05, 1.16)) and the proportion returned without chasing (RR 1.14 (95% CI 1.05, 1.24) were higher in the incentive group, and the overall non-response rate was lower (RR 0.68 (95% CI 0.53, 0.87)).Analysis of costs suggested a cost of 67.29 POUNDS per additional questionnaire returned.

View Article: PubMed Central - HTML - PubMed

Affiliation: Warwick Medical School Clinical Trials Unit, University of Warwick, Coventry, UK. s.gates@warwick.ac.uk

ABSTRACT

Background: Sending a monetary incentive with postal questionnaires has been found to improve the proportion of responders, in research in non-healthcare settings. However, there is little research on use of incentives to improve follow-up rates in clinical trials, and existing studies are inconclusive. We conducted a randomised trial among participants in the Managing Injuries of the Neck Trial (MINT) to investigate the effects on the proportion of questionnaires returned and overall non-response of sending a 5 pounds gift voucher with a follow-up questionnaire.

Methods: Participants in MINT were randomised to receive either: (a) a 5 POUNDSgift voucher (incentive group) or (b) no gift voucher (no incentive group), with their 4 month or 8 month follow-up questionnaire. We recorded, for each group, the number of questionnaires returned, the number returned without any chasing from the study office, the overall number of non-responders (after all chasing efforts by the study office), and the costs of following up each group.

Results: 2144 participants were randomised, 1070 to the incentive group and 1074 to the no incentive group. The proportion of questionnaires returned (RR 1.10 (95% CI 1.05, 1.16)) and the proportion returned without chasing (RR 1.14 (95% CI 1.05, 1.24) were higher in the incentive group, and the overall non-response rate was lower (RR 0.68 (95% CI 0.53, 0.87)). Adjustment for injury severity and hospital of recruitment to MINT made no difference to these results, and there were no differences in results between the 4-month and 8-month follow up questionnaires. Analysis of costs suggested a cost of 67.29 POUNDS per additional questionnaire returned.

Conclusion: Monetary incentives may be an effective way to increase the proportion of postal questionnaires returned and minimise loss to follow-up in clinical trials.

Trial registration number: ISRCTN61305297.

Show MeSH
Related in: MedlinePlus