BackgroundRed cell distribution width (RDW) reflects the variation in the circulating erythrocytes size (anisocytosis) that can increase in chronic inflammation due to ineffective erythropoiesis [1], while mean platelet volume (MPV) reveals the average size of platelets and may disclose its activation. Both are typically included in the complete blood count (CBC) and have been studied as a possible indicator of disease activity in many inflammatory conditions [2].ObjectivesThis study aimed to assess the relationship between MPV and RDW levels and various rheumatoid arthritis (RA) clinical,laboratory and ultrasongraphic disease activity parameters in patients with recent onset RA before and after initiation of therapy.MethodsWe assessed MPV and RDW in blood samples obtained from 60 recent onset RA patients and 30 healthy controls at baseline and 4 months after initiation therapy with non-biological disease modifying anti-rheumatic drugs (DMARDS). Disease activity was calculated using the 28 joint counts (DAS28) and musculoskeletal ultrasound examination (MSUS) was performed at baseline and after 4 months using a 12-joint score (bilateral elbow, wrist, 2nd metacarpophalangeal (MCP), 3rd MCP, knee, ankle) [2]; Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) levels, rheumatoid factor (RF) titre and anti-cyclic citrullinated peptide (anti-CCP) antibodies titre were measured and the health assessment questionnaire (HAQ) score was documented.ResultsBaseline RDW was significantly increased in RA (15.16 ± 3.63%) compared to its level in the healthy controls (12.16 ± 1.43%) (p<0.001). While, there was no significant difference in MPV between RA and control groups (10.92 ± 2.02 fl and 10.08 ± 0.88 fl respectively) (p=0.2).In RA patients, baseline RDW significantly correlated with CRP(r=0.39, p<0.05), DAS28 (r=0.47, p<0.05), grey scale (GS) (r=0.53, p<0.05) and power Doppler (PD) (r=0.56, p<0.001) synovitis scores. Also, RDW at 4 months follow up significantly correlated with the DAS28 (r =0.42, p<0.05), GS score (r=0.45, p<0.05). MPV showed no significant correlation with clinical, laboratory and ultrasonographic parameter of RA disease activity.Baseline RDW (p =0.02) was shown to be comparable to ESR (p =0.03) but less than CRP (p =0.001) at predicting PD synovitis score.ConclusionRheumatoid arthritis patients have significantly increased RDW levels that remarkably correlated with clinical, laboratory and MSUS parameters of inflammations suggesting that it could be a useful marker to reflect RA disease activity. RDW could be a useful biomarker to predict treatment outcome in RA patient. In this regard, MPV had poor correlations.References[1] Aksoy ŞN, Savaş E, Sucu M, Kisacik B, Kul S, Zengin O. Association between red cell distribution width and disease activity in patients with Behçet’s disease. J Int Med Res. 2015Dec;43(6):765-73.[2] Tecer D, Sezgin M, Kanık A, İncel NA, çimen öB, Biçer A, Şahin G. Can mean platelet volume and red blood cell distribution width show disease activity in rheumatoid arthritis?...