Response to: 'Correspondence on 'Prevotella copri in individuals at risk for rheumatoid arthritis'' by Sun and Ni.

We read with great interest the letter by Sun and Ni.1 Our study described an increased relative abundance in Prevotella spp in individuals at risk of rheumatoid arthritis (RA), particularly in ‘pre-clinical RA stages’, among participants enrolled in a cohort of first-degree relatives of patients with RA (SCREEN-RA).2 Our findings are consistent with the mucosal origins hypothesis of RA development.3 Sun et al explored whether single nucleotide polymorphisms (SNPs) associated with gut microbiome and derived from a genome-wide association study (GWAS) were also associated with RA. The authors performed a Mendelian randomisation (MR) analysis to assess potential associations of ‘gut microbiome-associated-SNPs’ with RA and concluded that there was no causal relation between gut microbiome and RA. We respectfully would like to highlight some substantial differences between our study and Sun et al ’s study and …