Horta-Baas G, et al. - In patients with osteoarthritis (OA), fibromyalgia (FM), rheumatoid arthritis (RA) and spondyloarthritis (SpA), authors sought to evaluate red blood cell distribution width (RDW) and assessed its clinical importance. In clinical practice, RDW interpretation is a useful tool in subjects with articular pain to distinguish between articular inflammatory and non-inflammatory joint diseases, as with C-reactive protein (CRP). Seemingly a surrogate marker of the inflammatory process was RDW. A six-fold increase in anisocytosis for the presence of a possible articular inflammatory disease was seen.