CRP and rheumatoid arthritis: Table 5 shows the results of both univariant and multivariant linear regression models investigating factors associated with claudin-1 levels in RA patients. It determined that CRP showed a significant negative association with claudin-1 levels in multivariate analyses (p = 0.045). Furthermore, when the multivariate analysis was restricted to the subgroup of patients with RA who had not achieved clinical remission, i.e., DAS28-ESR ≥ 3.2, the abundance of the genus Veillonella is positively associated with claudin-1 levels (p = 0.004) (Table 6).