Tumour Necrosis Factor Alpha Serum Levels and its Gene Polymorphism 850 C/T (rs1799724) as Prognostic Markers of Traumatic Brain Injury Outcome

Abstract

Introduction: Road traffic accidents have been responsible for the high incidence of head injuries. In a study from India, it was reported that there were 150 Traumatic Brain Injury (TBI) cases per 1,00,000 population, out of which 20 succumbed to death. In the repair process of TBI many chemicals play a role, of which, Tumour Necrosis Factor alpha (TNF-a) is important as TNF-a was shown to possess both neurotoxic and neuroprotective activity. Aim: To evaluate the serum levels of TNF-a and its functional polymorphism in TBI patients and assessing the outcome. Materials and Methods: The prospective cohort observational study was conducted in the Department of Genetics and Molecular Medicine, Kamineni Hospitals, Hyderabad, Telangana, India, from June 2008 to May 2012. It included 126 patients of both sexes with severe and moderate head injuries based on Glasgow Coma Scale (GCS) scores. A 3 mL of plain/Ethylenediaminetetraacetic acid (EDTA) blood sample was drawn from individuals immediately after admission, which was used for serum TNF-a assessment and DNA isolation for TNF-a genotype analysis. The TNF-a levels were measured by Enzyme Linked Immunosorbent Assay (ELISA) using KRISHGEN Biosystems (Catalog No. KB 100-HTNF a) kit. Outcome assessment was done based on Glasgow Outcome Scale (GOS). Statistical analysis was accomplished by Open Epi version 3.01 software. Odd’s Ratio (OR) were used to calculate risk of good/bad outcome with 95% confidence interval and results with a p<0.05 were considered statistically significant. Results: A total of 126 subjects of Indian origin were enrolled in this study. The mean age of the subjects was 36.7±12.97 years. Out of the 126 patients, 46.8% (59) had multiple lesions. The patients with <40 pg/mL (as per the kit specifications) TNF-a levels were 67.50% (85/126), while those with >40 pg/L were 32.50% (41/126). The most common genotype found in the TBI patients was TT with a frequency of 60.3% (76/126), followed by CT with a frequency of 16.6% (21/126) and CC with a frequency of 23% (29/126). When genotype and TNF-a serum levels were studied together, it was seen that low TNF-a level (11-40 pg/mL) was associated with C allele and CC genotype, while those with TT genotype had high TNF-a level (>40 pg/mL) when compared with other genotypes (CC, CT) and this was found to be statistically significant with an OR=3.4064, (95% CI= 1.8426 to 6.2975), p=0.0001. Higher percentage of death and disability was seen in patients with TT genotype while CC genotype showed good recovery at six months with OR=3.6441 (95% CI=1.911 to 6.946), p=0.0001. This suggests that T allele of TNF-a C850T polymorphism has a 3.6 fold higher risk of bad outcome in patients with TBI. Conclusion: The C allele and CC genotype of rs1799724 polymorphism was associated with positive outcome at three to six months. Thus, evaluating TNF-a levels and evaluating the genotype of rs1799724 polymorphism at admission, can be taken as prognostic marker. It can also be used as a target for therapeutic intervention.