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Randomized Controlled Trial
. 2018 Jan 5;18(1):3.
doi: 10.1186/s12874-017-0467-5.

Effects of pre-notification, invitation length, questionnaire length and reminder on participation rate: a quasi-randomised controlled trial

Marie Koitsalu  1 , Martin Eklund  2 , Jan Adolfsson  3 , Henrik Grönberg  2 , Yvonne Brandberg  4
Affiliations
Randomized Controlled Trial

Effects of pre-notification, invitation length, questionnaire length and reminder on participation rate: a quasi-randomised controlled trial

Marie Koitsalu et al. BMC Med Res Methodol. .

Abstract

Background: Improving participation rates in epidemiologic studies using questionnaires and biological sampling is important for the generalizability of the outcome. The aim of this study was to examine the effects of pre-notification, invitation length, questionnaire length, and reminder on participation rate and to investigate whether some factors contributed to participants doing both the questionnaire and blood sampling as oppose to only one part.

Methods: Our study was embedded within the pilot testing of a large population-based study about prostate cancer screening. Our study sample consisted of 28.134 men between 50 and 69 years of age and living in the region of Stockholm (Sweden) invited to respond to a web-based questionnaire and to provide blood for prostate cancer testing. The men were randomly allocated according to birth of date to receive either: (a) a pre-notification postcard or not; (b) a shorter or a longer invitation letter; (c) a shorter or a longer web-based questionnaire, and (d) a reminder or not. The effects of the survey design factors were tested using chi-square.

Results: The use of a pre-notification (p < 0.0001), a longer questionnaire (p = 0.004) and the use of a reminder (p = 0.02) were associated with an increase in overall participation, i.e. responding to the questionnaire or providing blood for PCT or performing both components.

Conclusions: The results of this pilot study justified the use of a pre-notification and a reminder in the following large population based study since the benefits of increased participation traded off against the greater costs incurred. Furthermore, we were able to use the longer version of the questionnaire, which allowed us to collect more information without risking a lower response rate.

Keywords: Invitation letter; Participation rate; Pre-notification; Questionnaire length; Reminder; Response rate.

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Conflict of interest statement

Ethics approval and consent to participate

Ethical approval for this study was obtained from the Regional Ethical Review Board in Stockholm (DNR 2012/572–31/1). All participants provided written informed consent.

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1
Fig. 1
Participation rates for each dispatch arms. * P-values of participation to one or two components are shown. a + = presence of pre-notification; − = absence of pre-notification. b + = long invitation letter; − = short invitation letter, c + = long questionnaire; − = short questionnaire. d + = presence of reminder; − = absence of reminder
See this image and copyright information in PMC

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