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June 21, 2022

CBC Biomarkers: Red Cell Distribution Width

Optimal Takeaways

The red cell distribution width (RDW) indicates whether there is a wide variation in the size of RBCs in circulation. Measurement of RDW assists in assessing anemia as well as cancer prognosis. Elevated RDW is also seen with cardiometabolic disease and inflammation and is often associated with nutritional deficiencies.

Conventional Lab Range: 11 - 15%

Optimal Dx’s Optimal Range: 11 - 12.6%    

Low RDW suggests uniformity in red blood cell width.

High RDW is associated with hemolytic anemias, posthemorrhagic anemia, hemoglobinopathies, and nutritional deficiency of iron, B12, or folate. Elevated RDW may also be observed in myelodysplastic syndrome, cancer, autoimmunity, chronic liver disease, metabolic syndrome, single nucleotide polymorphisms, and post-blood transfusion (Fava 2019). Increased RDW is associated with smoking and heart disease risk (Gang 2016), as well as inflammation and poorer cancer prognosis (Ai 2018).


Red cell distribution width reflects variations in the size of RBCs in circulation and is based on RBC and MCV values. It is useful in the classification of different types of anemias. Red blood cells are normally uniform in size, and a wide variation is associated with a condition called anisocytosis. Mounting evidence demonstrates an association between increased RDW and cardiovascular disease, diabetes, and cancer.

A comprehensive review of the literature found that elevated RDW was associated with biomarkers of inflammation (CRP, fibrinogen, WBCs), metabolic syndrome, dyslipidemia, CVD mortality, ischemic heart disease, hypertension, and peripheral artery disease, and diabetes mellitus (Fava 2019).

Increased risk of diabetes was observed in a retrospective study of 2,688 individuals as RDW rose above 12.2% (Gang 2016). In a prospective cohort study of 29,526 coronary angiography patients, the lowest rate of incident mortality was found in those with an RDW of 12.6% or less (Anderson 2007).

During follow-up of a large prospective study of 25,612, researchers noted that a 1% increase in RDW was associated with a 16% increased risk of a first myocardial infarction, even after adjusting for several variables and excluding those with anemia. An RDW above 13.7% was associated with a 69% greater risk of a first MI than those with an RDW of 10.7-12.2% (Skjelbakken 2014). Researchers hope to utilize RDW to help predict and prevent cardiovascular disease and cerebrovascular events (Li 2017).

RDW is considered a prognostic biomarker for both acute and chronic heart failure. In one prospective cohort study of 218 acute heart failure patients, the mean RDW was 15.3% for those with heart failure and diabetes, and 15.2% with heart failure but no diabetes. Researchers noted a 34.9% increased risk of all-cause mortality, or readmission for heart failure, for each 1% increase in RDW (Xanthopoulos 2017).

A higher RDW may be associated with a poorer prognosis in cancer including lung, breast, prostate, gastrointestinal, and hematological cancers. A meta-analysis of 7 studies comprising 1,031 subjects with hematological cancers, e.g., leukemia, lymphoma, and multiple myeloma, observed decreased survival as RDW rose above 14% (Ai 2018). Researchers note that RDW abnormalities may be related to the role that inflammation plays in impairing erythropoiesis.

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Ai, L., Mu, S., & Hu, Y. (2018). Prognostic role of RDW in hematological malignancies: a systematic review and meta-analysis. Cancer cell international, 18, 61.

Anderson, Jeffrey L et al. “Usefulness of a complete blood count-derived risk score to predict incident mortality in patients with suspected cardiovascular disease.” The American journal of cardiology vol. 99,2 (2007): 169-74. doi:10.1016/j.amjcard.2006.08.015

Fava, Cristiano et al. “The role of red blood cell distribution width (RDW) in cardiovascular risk assessment: useful or hype?.” Annals of translational medicine vol. 7,20 (2019): 581. doi:10.21037/atm.2019.09.58

Gang, Li, and Wan Lifang. “Association of the Elevated Red Blood Cell Distribution Width with the Risk of Developing Diabetes Mellitus.” Internal medicine (Tokyo, Japan) vol. 55,15 (2016): 1959-65. doi:10.2169/internalmedicine.55.5956

Li, Ning et al. “Red Blood Cell Distribution Width: A Novel Predictive Indicator for Cardiovascular and Cerebrovascular Diseases.” Disease markers vol. 2017 (2017): 7089493. doi:10.1155/2017/7089493

May, J. E., Marques, M. B., Reddy, V., & Gangaraju, R. (2019). Three neglected numbers in the CBC: The RDW, MPV, and NRBC count. Cleveland Clinic journal of medicine, 86(3), 167–172. [R]

Pagana, Kathleen Deska; Pagana, Timothy J.; Pagana, Theresa N. Mosby's Diagnostic and Laboratory Test Reference. Elsevier Health Sciences. 2019.

Skjelbakken, Tove et al. “Red cell distribution width is associated with incident myocardial infarction in a general population: the Tromsø Study.” Journal of the American Heart Association vol. 3,4 e001109. 18 Aug. 2014, doi:10.1161/JAHA.114.001109 [R]

Xanthopoulos, Andrew et al. “Red blood cell distribution width as a prognostic marker in patients with heart failure and diabetes mellitus.” Cardiovascular diabetology vol. 16,1 81. 6 Jul. 2017, doi:10.1186/s12933-017-0563-1

Tag(s): Biomarkers

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