Also, Naushad et al. [25] showed that the RFC1 80A-allele increased the usefulness of MTX therapy by 1.53-fold in their meta-analysis, which included 18 studies and was representative of 3592 RA individuals, and the 80AA-genotype raised the impact by 1.85-fold with an increased MTX dose equivalent to 15 mg/week, which is comparable to the average dose in the current study. This evidence concerns the gene RFC1 and rheumatoid arthritis.