INTERVAL is a randomised controlled trial in up to 50,000 blood donors being conducted within the framework of the UK’s National Blood and Transplant service (NHSBT). The main objectives are to determine whether blood can be safely collected more frequently than present practice, and whether donation intervals can be tailored to the individual’s capacity to give blood.
The INTERVAL study has been set up by the University of Cambridge and the University of Oxford in collaboration with the NHSBT.
As the UK population ages, the demand for blood transfusions is likely to increase. One approach to enhance blood supplies is to collect blood more frequently from existing donors. The limits set for donation frequency have been set to minimise iron deficiency in repeat blood donors. However, there is no strong scientific evidence to define how long this interval should be to optimise the number of blood units collected and donor well-being following donation. As a result, inter-donation intervals vary widely across Europe. In England men and women are invited to donate at 12 and 16 weeks respectively. This is a relatively long interval compared to other European countries in which donation frequency can be as often as every 8 weeks.
There is considerable inter-individual variation in iron stores, dietary intake, and efficiency of absorption which may affect the interval at which blood donations can be safely made in specific subgroups of donors.
The trial involves NHSBT staff, across the 25 permanent donation clinics in England, enrolling up to 50,000 whole-blood donors in a two-year intervention. We will implement methods to randomise men (n= ~ 25,000) to standard 12-wk vs. 10-wk vs. 8-wk inter-donation intervals and women (n= ~ 25,000) to standard 16-wk vs. 14-wk vs. 12-wk intervals. The primary end-point, to be assessed 2 years after recruitment, is donation rate/year and the key secondary endpoint is quality-of-life. The sample size has been calculated to reliably assess the impact of donation intervals on these outcomes in pre-specified subgroups of donors who may be more or less susceptible to iron deficiency with increased frequency of donation. Iron status will be measured through established (eg, ferritin and haemoglobin) and novel (eg, reticulocyte haemoglobin) biomarkers (reti.) Evidence for the impact of iron status on cognitive function (via internet-based fluid intelligence, attention and memory tasks) and exercise tolerance (via accelerometry) will also be explored. The cost-effectiveness of reducing donation intervals will be calculated and compared to alternatives to improve blood donation.
This trial has scope to optimise the blood donation experience and inform national policy on donation frequency. Added value is provided by this study’s creation of a national epidemiological bio-resource that will contribute to broader public health research.