Apolipoprotein E polymorphism and outcome after closed traumatic brain injury: influence of ethnic and regional differences

Abstract

OBJECT: The presence of the apolipoprotein E-epsilon4 (APOE-epsilon4) allele is reported to be associated with poor outcome after traumatic brain injury (TBI). This study was performed to determine if the presence of the APOE-epsilon4 allele influenced outcome in a cohort of black patients with TBI who had homogeneous neuropathological findings. METHODS: Venous blood was collected at the time of admission to determine the APOE genotype in black Zulu-speaking patients who presented with traumatic cerebral contusions. The frequency of the APOE-epsilon4 allele's appearance was correlated with outcome at a minimum of 6 months of follow up. Univariate and multivariate analyses were performed to determine independent risk factors and to control for confounding factors. In 110 black Zulu-speaking patients with traumatic cerebral contusions, genotypes for APOE were analyzed. Eleven of 45 (24.4%) with the APOE-epsilon4 allele experienced a poor outcome, compared with 10 (15.4%) of 65 without this allele (p = 0.34). Both patients with homozygous APOE-epsilon4 alleles experienced a good outcome (Glasgow Outcome Score 5). Univariate and multivariate analysis revealed no significant relationship in patients with the APOE-epsilon4 allele with regard to age, admission Glasgow Comas Scale score, contusion volume, type of neurosurgical management, and outcome. The risk of a poor outcome was, however, greater in patients with the APOE-epsilon4 allele (relative risk 1.59; 95% confidence interval 0.74-3.42). CONCLUSIONS: The authors recorded no relationship between APOE-epsilon4 allele status and outcome after TBI in black patients. Given the high regional susceptibility to the APOE gene, further studies, possibly even community-based investigations and studies conducted in other geographic areas, are probably warranted.