TNF and rheumatoid arthritis: Among these common polymorphisms in the promoter, a G-to-A transition at position −308 (rs1800629) has been most widely analyzed.[5] Some investigations have suggested that such allelic variations could have functional significance, but the results obtained have been inconsistent.[6] Several studies have examined the potential contribution of −308 G/A TNFA SNP to AS and RA susceptibility.[7–14] However, the results about the relationship of the TNF-α rs1800629 polymorphism with RA and AS are still inconclusive.