ABO blood group in aneurysmal subarachnoid haemorrhage—a pilot study

Purpose To evaluate the distribution and impact of ABO blood group on the baseline characteristics and clinical outcomes of patients presenting with aneurysmal subarachnoid haemorrhage (aSAH). Methods Retrospective, single-centre study of patients admitted to a neurosurgical department in the UK, with a diagnosis of spontaneous subarachnoid haemorrhage between May 2014 and January 2020. Patients were categorised by ABO blood type and by Rhesus status. Clinical outcomes such as initial bleeding, rebleeding, delayed cerebral ischaemia (DIND) and venous thromboembolism were analysed in relation to the size of their association with ABO blood type. Hospital mortality rate, Glasgow Outcome Score (GOS) — at discharge and 3 months post-ictus, requirement for ventriculoperitoneal shunt insertion, discharge destination and inpatient length of stay were also considered. Results Four-hundred twelve adult patients admitted with aSAH were included in our analysis. The distribution of ABO group or Rhesus status in our cohort did not differ significantly from the general population in the UK. Blood group A patients had a significantly increased risk of developing DIND, compared with non-blood group A patients ( OR , 1.88 [95% CI : 1.10–3.21]). Conclusions ABO blood type appears to influence aSAH sequelae. Blood group A patients are at highest risk of DIND following aSAH.