The INTERVAL study is a randomised controlled trial (RCT) in up to 50,000 whole-blood donors recruited at the 25 donation
centres across England. Over a period of two years, participants will be randomised to give blood either at their usual donation
intervals or more frequently. Current practice is to invite men and women to give whole blood every 12 and 16 weeks, respectively.
During or 8 weeks and women every 16, 14 or 12 weeks. At the end of the study, we will compare the amount of blood donated and
assessments of well-being between the different study groups.
INTERVAL is important because although demand for blood transfusions is increasing in England due to the needs of an ageing
population, blood supply is critically limited by difficulties in attracting and retaining donors. Blood donation services in
different countries have developed varying customs. England has a relatively long interval compared to other European countries
where the frequency is as low as every eight weeks for men and ten weeks for women.
The study's main objectives are to embed a RCT within the existing framework of NHSBT that will help to shape national donation
policy by determining:
- the optimum interval between donations, for men and women, that maximizes blood supply without unacceptably increasing
iron deficiency/anaemia and its potential complications
- whether blood donation intervals can be tailored to donors on the basis of demographic, haematological, genetic and
During INTERVAL men will be randomised to donate every 12, 10 or 8 weeks and women every 16, 14 or 12 weeks. These will be used
to measure biomarkers as well as genetic factors. Online questionnaires regarding health, lifestyle and cognitive function will
also be collected. A subset of participants will take part in a study of the impact of donation interval on physical activity
The Universities of Cambridge and Oxford in collaboration with NHSBT have set up interval. The study has ethical approval from
the Cambridge (East) Research Ethics Committee. Recruitment commenced on 11 June 2012 and has involved the staggered roll out
of donation centres at a rate of one per week. Recruitment is scheduled to run until March 2013 with completion of the study
by April 2015. The trial will not only provide evidence for optimum donation intervals but will also be the foundation for a
future programme of research in blood donation.
Contribution to patient and donor care or service development
The INTERVAL study is aligned with the NHSBT's long-term aims to:
- ensure the supply of blood by allowing a direct assessment of the effect of incremental increases in donation frequency
on blood collection yields
- improve the health and well-being of donors. Data from this study will inform tailoring of donation intervals to reduce
deferral rates and retain donors
- provide a more personalised approach to donation and reduce deferral rates due to iron deficiency and anaemia, and
- evolve into a leading evidence-based health organisation.