Red blood cell distribution width (RDW) is an objective measured value, which reflects the variability of circulating red blood cells (RBCs). In the past years, RDW has raised attention in the field of inflammation as it was associated with the outcomes of patients with autoimmune and cardiovascular diseases. Immune and inflammatory factors are involved in the pathogenesis of multiple sclerosis (MS) and loss of polyunsaturated fatty acids from plasma and blood cell membranes has been reported in MS patients, contributing to the variation of erythrocyte deformability. The relationship between MS and RDW is not well study.
This investigation aimed to assess the association between RDW and MS. Our goal was to compare baseline RDW to EDSS at 5 years of diagnosis and verify if it predicts worse disability.
A retrospective observational study was performed. We studied patients with Relapsing-remitting MS (RRMS) followed in the Neuroimmunology Clinic of a Portuguese Hospital that had at least one measuring of RDW at baseline. We included patients diagnosed with RRMS (between 2005-2015) according to the McDonald 2017 criteria. Patients with hematologic, oncological, infectious, and thyroid diseases, renal or hepatic dysfunction, or other autoimmune diseases were excluded.
82 patients with RRMS were included. 60 (73,2%) female, aged from 14 to 55 years old at diagnosis, with a mean of 33,56 (SD=20,21) years old. Eight (9,8%) patients had new T2 lesions in MRI at 5 years and 4 (4,9%) shown lesions capturing contrast at 5 years. Two (2,4%) patients had no treatment at 5 years, 62 (77,5%) first-line treatment and 18 (22,5%) second-line treatment. Correlations showed positive association of EDSS at 5 years with RDW at baseline (r=,451; p<,01), EDSS at baseline (r=,596; p<,01), age at diagnosis (r=,339; p<,01) and platelets at baseline (r=,401; p<,01). Multiple linear regression found increased disability (EDSS at 5 years) for patients undergoing second-line treatment (β=0,86; p=,003), and higher RDW at baseline (β=0,47; p=,007). Analyzing RDW results for quartiles, it was statistically significant for quartile 4 [13,5; 16,4[ (β=0,74; p=,039), suggesting that a very increased RDW at baseline is strongly associated with higher EDSS at 5 years.
Higher RDW at baseline is a predictor of worse disability at 5 years in RRMS patients. Furthermore, RDW equal to or higher than 13,5% is useful in identifying patients that will have a worse disability at 5 years in this study. Second-line treatment is also a determining factor of worse EDSS which is expected due to the use of these lines of treatment for the more aggressive disease. We believe more studies should be held to confirm this association once biomarkers determining disability can have an impact on the therapeutic approach and in this sense, are imperious.