Therefore, it is uncertain if the lower frequencies of carriers of PTPN22 rs2476601 and SE in our Spanish patients compared to patients in the previous studies conducted with participants of Northern European ancestry could have contributed to the discordant results (PTPN22 risk allele carriers in our RA patients =20.7% vs. 27.8% and 27.3% in NARAC-I and NARAC-II, respectively, P <10−4 for both comparisons; and 54.6% of SE carriers in our RA patients vs. 75.5% and 71.1% in the VARA and SONORA samples, P <10−15 and P <10−9, respectively). Here, PTPN22 is linked to rheumatoid arthritis.