SAT0111 RED CELL DISTRIBUTION WIDTH IS A MARKER OF EARLY RESPONSE TO METHOTREXATE IN RHEUMATOID ARTHRITIS

Background: Red blood cell distribution width (RDW) has recently emerged as a possible surrogate biomarker of inflammation. Its potential role as prognostic biomarker has not been evaluated yet in Rheumatoid Arthritis (RA). Objectives: The following study aims to evaluate the potential prognostic role of RDW in the prediction of early response to methotrexate (MTX). Methods: We performed a retrospective analysis of clinical records of patients affected by RA, according to ACR/Eular classification Criteria. The baseline RDW was recorded and correlated with disease activity scores and inflammatory markers. The response to treatment was evaluated at the 3-months follow-up visit according to Eular response criteria. Results: We selected 88 patients (58 females, 65.9%), with a median age of 62 [52-69] years. 61 patients were positive for Rheumatoid Factor (RF) and/or anticitrullinated antibodies – anti-CCP (69.3%). The median DAS28 for Erythrocyte sedimentation rate (DAS28ESR) at the diagnosis was 4.16 [3.33-5.00] while the median RDW was 14.0 [13.1-14.9]%. The baseline RDW was directly associated to CRP (ρ= 0.250; p=0.02), but not with ESR (p=0.32) or DAS28ESR (p=0.40). All the patients received methotrexate (MTX) at a median dose of 10 [10-15] mg/week, 79 (89.8%) also received prednisone (median dose 5 [5-10] mg/day) and 20 hydroxychloroquine in addition to MTX. A significant trend towards a larger RDW was reported from patients with a good Eular response at three months (13.5 [13.0-14.4]%) to those with a moderate response (14.0 [13.2-14.7]%) and finally to those with a poor response (14.6 [13.6-16.0]%; p=0.004). At logistic regression, RDW (p=0.02), but not CRP or ESR (p=0.70 and p=0.37 respectively), was a predictor of a good Eular response. Moreover, in a further logistic regression model, baseline RDW (p=0.03) and baseline DAS28ESR (p=0.0009) were the only predictors of a good Eular response at three months, while age, gender, MTX and prednisone dosage and seropositivity did not fit the model. After the treatment RDW significantly increases (14.7 [14.0-15.7]%) and the variation of RDW from baseline is inversely related to the variation of DAS28ESR (ρ= -0.263; p=0.02). The increase of RDW is significantly higher in patients with a good Eular response, with a trend towards a smaller increase in case of moderate and poor response (0.95 [0.35-1.35]% vs. 0.65 [0.1-1.9]% vs. 0.2 [-0.62-0.77]%; p=0.015). Conclusion: RDW is a promising predictor of early response to MTX in RA; in this context, it performs better than classical inflammatory markers. Moreover, RDW significantly increases after MTX initiation, proportionately to response to treatment, suggesting a potential role for RDW as a marker of MTX effectiveness. Disclosure of Interests: None declared