Alterations of the gut microbiome have been implicated in RA, but differences between seropositive and seronegative patients, and between seropositive RA and healthy controls, have not been systematically reviewed.<h4>Methods</h4>PubMed, Scopus, Web of Science, and the Cochrane Library were searched to July 2025 for observational studies of adult RA patients reporting RF and/or ACPA status with gut microbiome analysis. Here, PRTN3 is linked to rheumatoid arthritis.