The DAS28 score stands for Disease Activity Score in 28 joints. It is a quantitative measure used to assess the severity and activity of rheumatoid arthritis (RA). This score is calculated based on the examination of 28 specific joints, encompassing both swollen and tender joints, in addition to other factors like the patient's global health assessment and C-reactive protein (CRP) levels or erythrocyte sedimentation rate (ESR).