CXCL8 and rheumatoid arthritis: To minimize inter‐individual variability, we employed paired PB, SF, and synovial tissue collected from the same patients during the same time window to measure the expression levels of IL‐6 and IL‐8 (RA/OA‐FME from RA/OA 01–03, RA‐PB from RA 01‐19, OA‐PB from OA 01‐03, RA/OA‐SF from RA/OA 01–24).