In an exploratory analysis, patients receiving red blood cell transfusions from donors who later developed multiple spontaneous ICHs, and were assumed to have CAA, were at a significantly increased risk of developing spontaneous ICH themselves.
“This may suggest a transfusion-transmissible agent associated with some types of spontaneous ICH, although the findings may be susceptible to selection bias and residual confounding, and further research is needed to investigate if transfusion transmission of CAA might explain this association,” the investigators noted.
“We do not think that the findings motivate a change in practice, and we should not let these results discourage otherwise indicated blood transfusion,” said lead author Jingcheng Zhao, MD, PhD, with Karolinska University Hospital Solna, Stockholm.
The study was published online in the Journal of the American Medical Association.
Novel finding
Recent evidence suggests that CAA exhibits “prion-like” transmissivity, with reports of transmission through cadaveric pituitary hormone contaminated with amyloid-beta and tau protein, dura mater grafts, and possibly neurosurgical instruments.
CAA, which is characterized by the deposition of amyloid protein in the brain, is the second most common cause of spontaneous ICH.
The researchers hypothesized that transfusion transmission of CAA may manifest through an increased risk for spontaneous ICH among transfusion recipients given blood from a donor with spontaneous ICH. To explore this hypothesis, they analyzed national registry data from Sweden and Denmark for ICH in recipients of red blood cell transfusion from donors who themselves had ICH over the years after their blood donations, with the assumption that donors with two or more ICHs would likely have CAA.
The cohort included nearly 760,000 individuals in Sweden (median age, 65 years; 59% women) and 330,000 in Denmark (median age, 64 years; 58% women), with a median follow-up of 5.8 and 6.1 years, respectively.
Receiving red blood cell transfusions from donors who later developed multiple spontaneous ICHs was associated with a greater than twofold increased risk of developing spontaneous ICH, compared with receiving a transfusion from donors without subsequent ICH (hazard ratio, 2.73; P < .001 in the Swedish cohort and HR, 2.32; P = .04 in the Danish cohort).
“The observed increased risk of spontaneous ICH associated with receiving a red blood cell transfusion from a donor who later developed multiple spontaneous ICHs, corresponding to a 30-year cumulative incidence difference of 2.3%, is a novel finding,” the researchers wrote.
There was no increase in post-transfusion ICH risk among recipients whose donors had a single post–blood-donation ICH.
The findings were robust to several of the sensitivity analyses.
A “negative” control analysis of post-transfusion ischemic stroke (instead of ICH) found no increased risk among recipients of blood from donors who had single or multiple ICHs.
This study provides “exploratory evidence of possible transfusion-transmission of a factor that causes ICHs, but more research is needed to confirm and to understand the mechanism,” said Dr. Zhao.
The researchers noted that they did not directly assess CAA but expect it would be more common among donors who develop multiple spontaneous ICHs, “as CAA-related ICH has been reported to have a 7-fold increase for recurrent ICHs, compared with non–CAA-related ICH.”