Brain haemorrhage risk may transfer through blood transfusions, researchers say

Brain haemorrhages could be transmitted through blood transfusions. 

A study by the Karolinska Institute in Sweden revealed that patients who received blood from donors who later suffered brain haemorrhages, were more than twice as likely to suffer a brain haemorrhage themselves.

In a paper published in JAMA, experts believe some people could pass on a protein called amyloid beta, which accumulates along the tiny blood vessels of the brain, triggering a condition known as cerebral amyloid angiopathy (CAA).

A common cause of spontaneous, recurring brain haemorrhages is the vascular disease is CAA, which has a death rate of around 50%. 

More than one million patients from Sweden and Denmark who had red blood cell transfusions between 1970 and 2017 were studied by the researchers. 

They found that people who had blood from someone who later had multiple haemorrhages, had around 4% risk of a haemorrhage within 30 years, compared to less than 2% for everyone else.

But the risk is very low. Dr Gustaf Edgren, a researcher at the department of medicine, Karolinska Institute said: “Blood transfusions are relatively common, which makes possible negative effects an important public health issue. 

“However, in this case, it’s very unlikely that you’d suffer a brain haemorrhage from something transmitted through a transfusion.”

Previous studies have shown CAA can also be transferred between individuals through neurosurgery.

In 2018, University College London found that four adults who had brain surgery when younger had a build up of amyloid in their brains, which may have been passed on by contaminated surgical equipment.

The Swedish researchers now plan to study samples from the Danish Blood Donor Study biobank to see if they can find the misfolded proteins that they suspect are responsible.

They are also hoping to corroborate the hypothesis that the link between brain haemorrhage and blood transfusion concerns CAA, as confirmation is still needed. 

The plan is also to obtain CAT and MR scans from the affected donors and patients. 

"This study does not demonstrate causality, so the observed increase in risk could depend on other factors," says the study's first author Jingcheng Zhao from Dr Edgren's group at Karolinska Institutet. "More research is needed to confirm our findings and understand the potential underlying mechanism."

Researchers suggest that if they can spot the amyloid early enough they could screen out donors carrying it, which should protect people receiving transfusions.

Dr Jingcheng Zhao, also of the Karolinska Institute, said: “We are working on setting up a study where we can assess potential biomarkers.”

A wide variety of organisms, including bacteria, viruses, prions, and parasites can be transmitted through blood transfusions, and NHS scandals have seen HIV and hepatitis passed on in contaminated blood.

David Werring, professor of clinical neurology at University College London said there were a number of reasons to be cautious about the research. “The number of outcome events was small, limiting statistical power and precision,” he said.

“Blood transfusion recipients may not be representative of the general spontaneous ICH population as they will likely have had blood transfusion for an underlying condition or procedure [like diseases associated with anaemia, trauma, or had surgery]."

He added: “Nevertheless, these hypothesis-generating data should stimulate further research into possible transmissible factors associated with cerebral CAA.”