Blood donation saves many lives each year. Most people donating blood experience no side-effects and feel well afterwards, but some people may feel faint or dizzy – known as a vasovagal reaction.

One of the Impact Committee selections from this quarter is a randomised controlled trial that evaluated several commonly used methods to prevent such vasovagal reactions in blood donation compared to standard care.

Improving on current blood donation care

There are various ways that blood donation clinics try and reduce the chance of donors feeling unwell afterwards. In this study, researchers looked at whether changes to the usual approaches made a difference in reducing the risk of fainting following blood donation.

Rather than the standard 500ml drink of water before donating, donors were given an isotonic drink. The usual 2-minute rest time on a chair post-donation was extended to 3 minutes. Researchers also looked at modified applied muscle tension (AMT) exercises and providing reading materials that help people prepare for donation psychologically.

The study included almost every blood donor in England – over 1.3 million people – during the study period, and linked data to other sources to determine outcome events and side effects. This work represents a large collaboration between different NHS bodies and universities.

Although the committee more commonly reviews observational studies, we’ve recognised a randomised controlled trial as it made excellent use of routine national health data collected as part of donors’ regular blood donation process.

A smart approach to challenging research

Looking at the effectiveness of multiple interventions within the same study is challenging, which is why I was impressed by the way that the researchers approached their work. The trial has several interesting design features. Firstly, it is a factorial design, which allowed the researchers to assess the effect of multiple interventions on the outcome using a single experiment. Depending on the intervention, they used different design features best suited.

For example, the psychological intervention and applied muscle tension exercises cannot be unlearned by donors or staff once they know them. This could make it difficult to draw comparisons between people receiving and not receiving these interventions once introduced.

To circumvent this, the researchers used a so-called stepped wedge design – a type of phased roll out where eventually all participants will receive the intervention, but the time at which the intervention is introduced in a blood bank is randomised.

The isotonic drink and chair time interventions used one-period and two-period crossover designs. In a traditional scientific trial, one group gets the new treatment (the test group), and another group gets the standard treatment (the control group), and they stay in those groups for the entire study.

In a crossover trial, the groups take turns. So, instead of a donation centre testing the isotonic drink or the 3-minute chair time for the entire three years, sites switched back and forth between providing the new interventions and returning to the standard practice (plain water or a 2-minute rest). This made the researchers more confident that any change they saw was due to the interventions rather than any specific characteristic of the donation clinics.

A “negative” result is a good result

Ultimately, the study found that none of the approaches were more effective than the standard practice at reducing fainting and dizziness following blood donation. This could be interpreted as a negative finding, but it’s still important to publish both “positive” and “negative” findings so that they can be learnt from.

In this case, the negative findings could also have a large impact on blood donations. They give reassurance that current standard practice is sufficient and may reduce resource use across blood donations nationwide.

Read the study