Association between polymorphisms within the gene coding for tumor necrosis factor (TNF)-alpha with outcomes of treatment in a sample of Iraqi patients with ankylosing spondylitis taking etanercept: an observational study

Background: Ankylosing spondylitis (AS) is a progressive, chronic inflammatory illness with an unclear etiology that explicitly targets the vertebral column, peripheral joints, and extraarticular tissues. The purpose of this research was to investigate if the existence of single nucleotide polymorphisms (SNPs) in the promoter region of the tumor necrosis factor-alpha (TNF-α) gene at positions -1031T/C (rs199964), -857C/T (rs1799724) and -806C/T (rs4248158) in a sample of Iraqi AS patients could influence the patients' outcomes with etanercept. Methods: Sixty patients with established AS receiving only etanercept were selected to enroll in this study, with a mean age of 40.75±8.67 years; 51 patients were male. Patients were classed as "responders" if they obtained a Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) 50 clinical response and as "non-responders" if they did not achieve a BASDAI 50 clinical improvement after at least six months of treatment. After polymerase chain reaction (PCR) product amplification of the purified blood DNA, the promoter region of TNF-α gene SNPs was established by Sanger sequencing. Results: This research found a significant difference in the TT genotype of rs1799964, P = 0.02, in the responder group, in contrast to the TC genotype of rs1799964, which was significantly more frequent in the non-responder group, P = 0.01. The wild TT genotype of rs1799964 seemed to enhance the probability of being a responder. Nevertheless, the heterozygote TC genotype of rs1799964 showed a negative and significant correlation for responsiveness to etanercept. Conclusion: The TT genotype of rs1799964 is associated with a higher likelihood of responding to ETN, suggesting that it is a valuable diagnostic for predicting response in Iraqi AS patients.