ABO blood type and functional neurological outcome in patients with severe traumatic brain injury

Background: The ABO blood system has been involved in the pathogenesis of several diseases, including coagulopathy and bleeding complications. In trauma patients, blood type A has been associated with acute respiratory distress syndrome, and recently, blood type O has been associated with all-cause mortality. The purpose of this study was to assess the association between ABO blood types and long-term functional outcomes in critically ill patients with severe traumatic brain injury (TBI).

Methods: We conducted a single-center, retrospective, observational study including all patients admitted to the intensive care unit with severe TBI (defined as a Glasgow Coma Scale score of ≤8) between January 2007 and December 2018. Patient characteristics and outcomes were extracted from a prospective registry of all intubated patients admitted to the intensive care unit for TBI. ABO blood types were retrospectively retrieved from patient medical records. The association between ABO blood type (A, B, AB, and O) and unfavorable functional outcome (defined by a Glasgow Outcome Scale score between 1 and 3) 6 months after injury was assessed in univariate and multivariate analysis.

Results: A total of 333 patients meeting the inclusion criteria were included. There were 151 type O (46%), 131 type A (39%), 37 type B (11%), and 12 type AB patients (4%). No significant differences in baseline demographic, clinical, or biological characteristics were observed between blood types. The prevalence of unfavorable outcome was significantly different between the four groups. After adjustment for confounders, blood type O was significantly associated with unfavorable outcome at 6 months (odds ratio, 1.97; confidence interval [1.03-3.80]; p = 0.042). The prevalence of coagulopathy or progressive hemorrhagic injury was not statistically different between blood types ( p = 0.575 and p = 0.813, respectively).

Conclusion: Blood type O appears to be associated with unfavorable long-term functional outcome in critically ill patients with severe TBI. Further studies are needed to detail the mechanism underlying this relationship.

Level of evidence: Prognostic and Epidemiological; Level IV.