From the Guidelines
Elevated RDW is a significant indicator of underlying health issues, and its management should focus on identifying and treating the root cause, with iron deficiency being a common cause, as indicated by a study published in 2021 1. Elevated RDW values are typically above 14.5%, and this condition is known as anisocytosis. The causes of elevated RDW are diverse and include:
- Iron deficiency anemia
- Vitamin B12 or folate deficiency
- Hemolytic anemia
- Recent blood transfusions
- Chronic inflammatory conditions
- Liver disease
- Certain cancers
- Myelodysplastic syndromes Further testing is necessary to determine the underlying cause of elevated RDW, and this may involve:
- Complete blood count (CBC)
- Peripheral blood smear
- Iron studies
- Vitamin B12 and folate levels
- Other tests depending on symptoms and medical history According to a study published in 2015 1, a wide size range of red cells, indicated by a high RDW, can help identify iron deficiency, especially in situations where microcytosis and macrocytosis co-exist. Treatment of elevated RDW should focus on addressing the underlying cause, such as iron supplements for iron deficiency or vitamin B12 injections for B12 deficiency, rather than treating the elevated RDW itself 1. In children, the assessment of iron status relies on a combination of biochemical indicators, including serum ferritin, transferrin saturation, and soluble transferrin receptor, as well as emerging tools like hepcidin concentrations 1. In clinical practice, it is essential to interpret RDW values in conjunction with other laboratory tests and clinical findings to provide accurate diagnosis and treatment, as elevated RDW alone is not a diagnosis but rather a clue that requires further investigation by a healthcare provider 1.
From the Research
Elevated RDW: Associations and Implications
Elevated Red Cell Distribution Width (RDW) has been associated with various health conditions and outcomes. The following points summarize the key findings:
- Elevated RDW is associated with higher mortality risk in the general population 2.
- In hemodialysis patients, higher RDW is associated with incrementally higher mortality risk, and RDW is a stronger predictor of mortality than traditional laboratory markers of anemia 2.
- RDW changes have been studied in patients with untreated pernicious anemia, showing that a large proportion of patients have normal RDWs, and elevation of RDW is not necessarily the earliest indicator of vitamin B12 deficiency 3.
- Deficiency testing for iron, vitamin B12, and folate is necessary for the production of red blood cells, and laboratory measurement of these concentrations can help in the differential diagnosis of anemic patients 4.
- Elevated RDW is associated with decreased ventilator-free days in critically ill patients, suggesting a relationship between RDW and pulmonary outcomes in the ICU 5.
- Combined cobalamin and iron deficiency anemia can be diagnosed using a model based on age and homocysteine assessment, highlighting the importance of evaluating serum vitamin B12 in patients with iron deficiency anemia over 60 years old 6.
Potential Causes and Associations
Some potential causes and associations of elevated RDW include:
- Iron deficiency anemia 3, 4, 6
- Vitamin B12 deficiency 3, 4, 6
- Folate deficiency 4
- Hemodialysis patients 2
- Critically ill patients 5
- Pernicious anemia 3
Laboratory Markers and Diagnostic Approaches
The following laboratory markers and diagnostic approaches are relevant to elevated RDW: