Red blood cell distribution width (RDW) – A new nutritional biomarker to assess nutritional risk and response to nutritional therapy?

Red cell distribution width (RDW) has been proposed as a surrogate marker for acute and chronic diseases and may be influenced by nutritional deficits. We assessed the prognostic value of RDW regarding clinical outcomes and nutritional treatment response among medical inpatients at nutritional risk.This is a secondary analysis of EFFORT, a randomized, controlled, prospective, multicenter trial investigating the effects of nutritional support in patients at nutritional risk in eight Swiss hospitals. We examined the association between RDW and mortality in regression analysis.Among 1,244 included patients (median age 75 years, 46.6 % female), high RDW (≥15 %) levels were found in 38 % of patients (n = 473) with a significant association of higher malnutrition risk [OR 1.48 (95%CI 1.1 to 1.98); p = 0.009]. Patients with high RDW had a more than doubling in short-term (30 days) mortality risk [adjusted HR 2.12 (95%CI 1.44 to 3.12); p < 0.001] and a signficant increase in long-term (5 years) mortality risk [adjusted HR 1.73 (95%CI 1.49 to 2.01); p < 0.001]. Among patients with high RDW, nutritional support reduced morality within 30 days [adjusted OR 0.56 (95%CI 0.33 to 0.96); p = 0.035], while the effect of the nutritional intervention in patients with low RDW was markedly smaller.Among medical patients at nutritional risk, RDW correlated with several nutritional parameters and was a strong prognostic marker for adverse clinical outcomes at short- and long-term, respectively. Patients with high baseline RDW levels also showed a strong benefit from the nutritional intervention. Further research is needed to understand whether monitoring of RDW over time severs as a nutritional biomarker to assess effectiveness of nutritional treatment in the long run.ClinicalTrials.gov Identifier: NCT02517476.