Clinical utility of red blood cell distribution width in inflammatory and non‐inflammatory joint diseases

Aim Current studies demonstrate red blood cell distribution width ( RDW ) as a possible surrogate biomarker of inflammation. The objectives of the present study were to examine RDW in patients with osteoarthritis ( OA ), fibromyalgia ( FM ), rheumatoid arthritis ( RA ) and spondyloarthritis (SpA) and to evaluate its clinical importance. Methods Six hundred and ninety‐nine ambulatory patients were evaluated. RDW , hemoglobin, erythrocyte sedimentation rate ( ESR ) and C‐reactive protein ( CRP ) were assessed. In order to compare groups, a Kruskall–Wallis test with post hoc Dunn's test was applied. A multiple logistic regression analysis was used to evaluate anisocytosis explanatory variables. Results Red blood cell distribution width values differed significantly among groups. Post hoc analysis demonstrated a significant increase in RDW within RA versus OA groups ( P < 0.001), active SpA versus OA ( P < 0.001), RA versus FM ( P < 0.001) and active SpA versus FM groups ( P = 0.001). Presence of anisocytosis was useful to discriminate between active articular inflammatory versus non‐inflammatory diseases with 48–95% sensitivity and 66–95% specificity. Multivariate analysis showed a six‐fold increase in anisocytosis for the presence of a possible articular inflammatory disease. Conclusion In subjects with articular pain, RDW interpretation is a useful tool in clinical practice to distinguish between articular inflammatory and non‐inflammatory joint diseases, as with CRP . RDW seems to be a surrogate marker of the inflammatory process.