Condition category
Not Applicable
Date applied
Date assigned
Last edited
Retrospectively registered
Overall trial status
Recruitment status

Plain English Summary

Background and study aims
We are carrying out a study of 50,000 blood donors to compare different intervals between blood donations. Our goal is to find the optimum interval for which it is safe for different donors to give blood. We will want to look at whether intervals should be tailored by age, gender, genetic profile, and other characteristics. The study's findings should help to improve the well-being of future blood donors in England and enhance the country's blood supplies.

Who can participate?
The INTERVAL study aims to recruit about 25,000 men and about 25,000 women, age > 17 years from NHS Blood and Transplant (NSHBT) blood donation clinics across England.

What does the study involve?
Over a period of two years participants will be invited to give blood either at usual donation intervals or more frequently. Men will be invited to donate every 12, 10 or 8 weeks and women every 16, 14 or 12 weeks. The donation interval to which a participant is allocated to will be decided by a process called ‘randomisation’, which is like a coin toss. At the end of the study, we will compare the amount of blood donated and measures of well-being in people asked to give blood at standard intervals versus those asked to give blood more frequently. We are inviting healthy blood donors who usually give blood at one of the permanent donation centres across England. As this has been designed as an almost paper-less trial only donors who have internet access and an email address are able to join.

What are the possible benefits and risks of participating?
There will be no immediate direct benefit to those taking part. But there should be benefits to future blood donors and to the country's future blood supply because the results of the study are likely to influence how the NHSBT collects blood donations. The main risk of giving blood more frequently is iron deficiency and the related anaemia because of a low haemoglobin level. Therefore, NHSBT will continue to follow its routine safety procedures to monitor haemoglobin level before donation. Participants will receive the usual ‘finger-prick’ screening test for haemoglobin levels and will need to be within the safe range to be eligible to donate.

Where is the study run from?
The INTERVAL study has been set up by the Universities of Cambridge and Oxford in collaboration with NHSBT.

When is study starting and how long is it expected to run for?
It is anticipated that recruitment will start mid-2012. Participants will be enrolled on the study for a period of two years; however, the study will extend beyond this as we intend to look at participants’ health over many years to assist future studies about the health of blood donors.

Who is funding the study?
Funding has been provided by NHSBT. If the 1-year initial phase of the study is concluded satisfactorily, then further funding is expected from NHSBT to complete the study. Once funding stops, data and samples collected during the study will be maintained, as a national collection, by the lead academic institution, the University of Cambridge, in partnership with NHSBT.

Who is the main contact?
1. Prof. John Danesh (
2. Prof. David Roberts (

Trial website

Contact information



Primary contact

Prof John Danesh


Contact details

Head of Department of Public Health and Primary Care
University of Cambridge
Wort's Causeway
United Kingdom

Additional identifiers

EudraCT number number

Protocol/serial number


Study information

Scientific title

A randomised trial to determine whether the interval between blood donations in England can be safely and acceptably decreased



Study hypothesis

It is hypothesised that the number of donations made by English blood donors will be greater with reduced vs. standard inter-donation intervals. The null hypothesis is that there will be no difference in donations between treatment groups; this may arise if reduced inter-donation intervals result in a greater number of donation deferrals (due to low haemoglobin) and/or an unacceptable burden to donors.

Ethics approval

NRES Committee East of England - Cambridge East, 16/02/2012, ref: 11/EE/0538

Study design

Two-year open randomised parallel-group multi-site trial

Primary study design


Secondary study design

Randomised controlled trial

Trial setting


Trial type


Patient information sheet

The patient information sheet is available on the trial website


Optimum intervals for blood donation


The study will involve 25,000 male and 25,000 female whole blood donors recruited at donation visits to the 25 permanent NHSBT clinics across England. Participation will be over a two-year period.

Male participants will be assigned to standard 12-week vs. 10-week vs. 8-week inter-donation intervals and female participants to 16-week vs. 14-week vs. 12-week intervals.

Intervention type



Not Applicable

Drug names

Primary outcome measures

Total blood collected after two years, expressed in units (470ml) per person per year

Secondary outcome measures

Assessed two years after recruitment and will include:
1. Donor quality of life using the SF-36 health survey (this is the key secondary outcome)
2. Number of donation 'deferrals' (i.e. temporary rejections) of donors due to low haemoglobin and other factors
3. Markers of iron status (serum ferritin and reticulocyte haemoglobin)
4. Cognitive ability (reasoning, attention and memory)
5. Levels of physical activity
6. Cost effectiveness
7. Donor attitudes, beliefs and values

Overall trial start date


Overall trial end date


Reason abandoned


Participant inclusion criteria

1. Age >17 years and fulfilling all normal criteria for blood donation
2. Willing to be assigned to any of the study intervention groups
3. Registered at one of the permanent donation clinics at the time of enrolment

Participant type

Healthy volunteer

Age group




Target number of participants


Participant exclusion criteria

Current exclusion criteria as of 22/05/2012
1. As the aim of the study is to be almost “paper-less”, it will involve remote web-based data collection. Hence, participants who do not have internet access and/or are not willing to provide an email address for study correspondence will be excluded

Previous exclusion criteria
1. Donors who are providing extra samples to NHSBT at their initial visit (e.g. for the British bone marrow registry) as there will be insufficient blood left in the sample pouch for the collection of study samples
2. As the aim of the study is to be almost “paper-less”, it will involve remote web-based data collection. Hence, participants who do not have internet access and/or are not willing to provide an email address for study correspondence will be excluded
3. Donors who have been identified for ‘special panels’ by NHSBT

Recruitment start date


Recruitment end date



Countries of recruitment

United Kingdom

Trial participating centre

University of Cambridge
United Kingdom

Sponsor information


NHS Blood and Transplant (NHSBT) (UK)

Sponsor details

c/o Professor Marion Scott
National R&D Manager
500 North Bristol Park
BS34 7QH
United Kingdom

Sponsor type




Funder type


Funder name

NHS Blood and Transplant (NHSBT) (UK) (ref: 11-01-GEN)

Alternative name(s)

Funding Body Type

Funding Body Subtype


Results and Publications

Publication and dissemination plan

Not provided at time of registration

Intention to publish date

Participant level data

Not provided at time of registration

Results - basic reporting

Publication summary

2014 protocol in:
2016 results in:

Publication citations

  1. Protocol

    Moore C, Sambrook J, Walker M, Tolkien Z, Kaptoge S, Allen D, Mehenny S, Mant J, Di Angelantonio E, Thompson SG, Ouwehand W, Roberts DJ, Danesh J, The INTERVAL trial to determine whether intervals between blood donations can be safely and acceptably decreased to optimise blood supply: study protocol for a randomised controlled trial., Trials, 2014, 15, 1, 363, doi: 10.1186/1745-6215-15-363.

Additional files

Editorial Notes

21/09/2016: Publication reference added.