Red blood cell distribution width: a promising index for estimating activity of autoimmune disease

Red blood cell distribution width (RDW) is a traditional hematological index used to explore the etiology of anemia. During past years, association between RDW and non-hematological diseases has attracted much attention. Accumulated evidence has revealed that RDW is elevated in various autoimmune diseases and associates with disease activity or complications. Here, I summarized the evidence concerning clinical utility of RDW in autoimmune diseases, including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), primary Sjogren's syndrome (pSS), inflammatory bowel disease (IBD), inflammatory myopathy (IM) and primary biliary cholangitis (PBC). Available evidence has supported that RDW is a useful index to estimate the activity in various autoimmune diseases. Further prospective cohort studies are needed to explore the prognostic value of RDW in autoimmune diseases.