CHI3L1 and rheumatoid arthritis: In patients with RA, Chi3l1 levels closely correlate with rheumatoid factor (RF) levels, RA activity (e.g., 28-joint disease activity score (DAS28), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) level), proinflammatory cytokines (e.g., tumor necrosis factor-α (TNF-α) and interleukin-1B (IL-1β)), and immunological markers of joint destruction such as matrix metalloproteinase-3 (MMP-3) [240,245,246].