What is the effect of different incentive levels on the participation rate for a mailed survey and telephone interview?

ISRCTN	ISRCTN95158258
DOI	https://doi.org/10.1186/ISRCTN95158258
Secondary identifying numbers	N/A

Submission date: 14/08/2013
Registration date: 04/10/2013
Last edited: 07/10/2013

Recruitment status: No longer recruiting
Overall study status: Completed
Condition category: Nutritional, Metabolic, Endocrine

Prospectively registered

Protocol

Statistical analysis plan

Results

Individual participant data

Record updated in last year

Plain English summary of protocol

Background and study aims
Non-response is an important issue for studies using a written questionnaire. For different reasons, potential participants are reluctant to complete questionnaires. Our aim is to find the best possible level of incentive (when using a written questionnaire and additional telephone interview) to participate in a study.

Who can participate?
Patients with diabetes who are aged 18 years or over can participate in this study.

What does the study involve?
Patients are randomly allocated to one of four groups. Patients are offered four different levels of incentive (either 5, 7.50, 10 or 12.50 euros, according to the group that they are allocated to) to participate in a written survey and an additional telephone interview.

What are the possible benefits and risks of participating?
All patients are part of the study, even if they do not participate (as we are studying the participation rate). The benefit for those who do participate is a gift card with a value of between 5 and 12.50 euros. There are no risks involved.

Where is the study run from?
This study is run from 7 GP practices; 5 of them in the city of Arnhem and 2 in the region Achterhoek (including the towns Aalten and Gendringen), Netherlands.

When is study starting and how long is it expected to run for?
Recruitment of patients started in June 2013 and will last until August 2014.

Who is funding the study?
The study is funded by the European Union, Belgium.

Who is the main contact?
Mr Jan Koetsenruijter, j.koetsenruijter@iq.umcn.nl
Professor Michel Wensing, m.wensing@iq.umcn.nl

Contact information

Prof Michel Wensing
Scientific

Geert Grooteplein 21
Nijmegen
6500 HB
Netherlands

Study information

Study design	Randomized controlled trial
Primary study design	Interventional
Secondary study design	Randomised controlled trial
Study setting(s)	GP practice
Study type	Screening
Participant information sheet	Not available in web format, please contact j.koetsenruijter@iq.umcn.nl to request a patient information sheet
Scientific title	The effect of different incentive levels on the participation rate for a mailed survey and telephone interview: a randomized controlled trial
Study objectives	Higher incentives will lead to a higher response rate, but this effect is not linear. For example, the relative increase of response will become smaller as the incentive becomes higher. Moreover, we expect this curve to be different between high and low deprivation areas.
Ethics approval(s)	Committee on Research Involving Human Subjects (CMO) region Arnhem - Nijmegen (Commissie Mensgebonden Onderzoek [CMO] regio Arnhem Nijmegen), 08/04/2013, ref: 2013/098
Health condition(s) or problem(s) studied	Participation rate within patients with type 2 diabetes
Intervention	Patients are randomized within a GP practice. At the GP practice the patient is handed over an anonymous and closed envelope with a specific level of incentive and a questionnaire included. Both researcher and the employee at the GP practice do not know the level of the included incentive. Respondents are offered four different levels of incentive to participate in a written survey and an additional telephone interview. The incentives are 5, 7.50, 10 and 12.50 euros. This is the only difference between the four treatment arms. There is no follow-up planned.
Intervention type	Other
Primary outcome measure	Participation rate will be studied within three different areas with different levels of deprivation (subgroup analysis). The participation rate is measured by the total amount of completed questionnaires and telephone interviews, divided by the total number of distributed questionnaires. This rate will be calculated for each level of incentive. There is only one time point as each participant can only complete the questionnaire once.
Secondary outcome measures	Not provided at time of registration
Overall study start date	01/06/2013
Completion date	01/08/2014

Eligibility

Participant type(s)	Patient
Age group	Adult
Lower age limit	18 Years
Sex	Both
Target number of participants	300
Key inclusion criteria	1. Medical diagnosis of diabetes (not a patient-reported diagnosis) 2. Type 2 diabetes only (no type 1, but comorbidities such as cardiovascular disease are allowed) 3. Male and female, 18 years or over
Key exclusion criteria	1. No established diagnosis of diabetes, but obesity or high risk for developing diabetes 2. Mix of type 2 and type 1 (not pure type 2 diabetes) 3. Pregnancy 4. Pregnancy-related diabetes 5. Recent/current major surgery or medical procedures 6. Severe cognitive or psychiatric handicap 7. Terminal illness/receiving palliative care 8. Absence of translators (e.g. family members) for patients with insufficient language skills
Date of first enrolment	01/06/2013
Date of final enrolment	01/08/2014

Locations

Countries of recruitment

Netherlands

Study participating centre

Geert Grooteplein 21

Nijmegen
6500 HB
Netherlands

Sponsor information

Radboud University Medical Centre (Netherlands)
Hospital/treatment centre

Postbus 9101
Nijmegen
6500 HB
Netherlands

Website	http://www.umcn.nl
"ROR"	https://ror.org/05wg1m734

Funders

Funder type

Government

European Union (Belgium)

No information available

Results and Publications

Intention to publish date
Individual participant data (IPD) Intention to share	No
IPD sharing plan summary	Not provided at time of registration
Publication and dissemination plan	Not provided at time of registration
IPD sharing plan