To evaluate the significance of red blood cell distribution width (RDW) and other factors for the disease activity in rheumatoid arthritis (RA).
Each patient underwent clinical examination and blood sampling for assessment of serum high-sensitivity C-reactive protein (hs-CRP) levels, erythrocyte sedimentation rate (ESR), hemoglobin concentration (Hb), hematocrit (HCT), RDW, and other erythrocyte parameters (mean corpuscular volume [MCV], mean cell Hb [MCH], mean corpuscular Hb concentration [MCHC]). Rheumatoid factors (RF-IgA, -IgG, -IgM) and anti-cyclic citrullinated protein antibodies (anti-CCP) were purified from the plasma and detected by ELISA. RA patients were divided into two groups based on DAS28 scores: active RA group (DAS28 > 5.1) and inactive RA group (DAS28 2.6 - 3.2).
Patient samples were within normal ranges for Hb (15.2 ± 1.3 g/L), HCT (29.9 ± 2.2%), and other red blood cell (RBC) parameters (MCV 80.3 ± 12.1 fL, MCH 26.6 ± 3.5 pg, MCHC 323 ± 25 g/L). The RDW was higher in the active RA group than in the inactive group (16.5 ± 3.2 vs. 13.9 ± 1.5%, p < 0.01). Similarly, the proportion of patients positive for RF and anti-CCP was higher in the active group than in the inactive group (RF 62 vs. 53%, CCP 83 vs. 61%). RF and anti-CCP were present at higher titers in patients with active RA. The bone erosion rate in the 110 RA patients was 67%. Patients with erosion had higher RDW than those without erosion (17.1 ± 2.2 vs. 13.9 ± 3.5%). High titers of anti-CCP and RF-IgM, -IgG, and -IgA were also associated with high bone erosion rates (67%, 77%, 67%, and 73%, respectively).
Our results suggest an association between RDW and levels of inflammatory factors and autoantibodies in RA. This association may be linked to the underlying proinflammatory state and increased oxidative stress, both of which correlate with impaired erythrocyte maturation. RDW, RF, and anti-CCP are key players in the proinflammatory and proatherogenic status of RA, and they may represent useful markers to improve characterization of disease activity in RA patients, thereby helping the clinician to define more appropriate therapeutic strategies.