From the Guidelines
Elevated RDW is a significant indicator of underlying health issues, such as iron deficiency anemia, vitamin B12 or folate deficiency, and requires prompt evaluation and treatment to prevent adverse outcomes on morbidity, mortality, and quality of life. The most recent and highest quality study 1 suggests that a comprehensive approach to diagnosing the cause of elevated RDW should include a complete blood count, iron studies, vitamin B12 and folate levels, and possibly thyroid function tests.
Key Considerations
- Elevated RDW indicates increased variation in red blood cell size, which can be caused by various factors, including iron deficiency anemia, vitamin B12 or folate deficiency, recent blood loss, hemolytic anemia, certain medications, liver disease, and chronic inflammatory conditions 1.
- The diagnosis of iron deficiency anemia can be challenging, especially in the presence of inflammation, and requires a combination of biochemical indicators, including serum ferritin, transferrin saturation, and soluble transferrin receptor 1.
- Treatment of elevated RDW should target the underlying cause, such as iron supplements for iron deficiency or vitamin B12 injections for B12 deficiency, and regular follow-up with a healthcare provider is essential to monitor response to treatment.
Diagnostic Approach
- A complete blood count with MCV, reticulocytes, serum ferritin, transferrin saturation, and CRP should be included in the minimum workup for elevated RDW 1.
- Additional tests, such as vitamin B12, folic acid, haptoglobin, and bone marrow smear, may be necessary to determine the underlying cause of elevated RDW 1.
- The use of emerging biomarkers, such as hepcidin and reticulocyte Hb content, may provide additional diagnostic value in certain cases 1.
Treatment and Management
- Treatment of elevated RDW should focus on addressing the underlying cause, rather than the elevated RDW itself, and may involve iron supplements, vitamin B12 injections, or other targeted therapies 1.
- Regular follow-up with a healthcare provider is crucial to monitor response to treatment and adjust the treatment plan as needed.
From the Research
Elevated RDW: Causes and Implications
- Elevated Red Blood Cell Distribution Width (RDW) is a parameter that reflects the degree of heterogeneity of erythrocyte volume, and is used in laboratory hematology for differential diagnosis of anemias 2
- An increased RDW has been associated with various human disorders, including cardiovascular disease, venous thromboembolism, cancer, diabetes, and chronic obstructive pulmonary disease 2
- Elevated RDW is also a strong and independent risk factor for death in the general population, and conveys important information for short- and long-term prognosis 2, 3
Association with Cardiovascular Disease
- Elevated RDW has been linked to an increased risk of cardiovascular events and mortality, and can be regarded as an index of enhanced patient fragility and higher vulnerability to adverse outcomes 3, 4
- RDW can be used as a prognosticator among persons with stroke, and is associated with stroke occurrence and strongly predicts both cardiovascular and all-cause deaths in persons with known stroke 3
Diagnostic Approach
- A diagnostic approach using a model based on age and homocysteine assessment can be used to differentiate between iron deficiency anemia and combined cobalamin and iron deficiency anemia 5
- Serum vitamin B12 should be evaluated in iron deficiency anemia patients over 60 years, as vitamin B12 deficiency is demonstrated in many patients with low vitamin B12 and iron deficiency anemia 5
Underlying Metabolic Abnormalities
- Elevated RDW can be attributed to a variety of underlying metabolic abnormalities, including shortening of telomere length, oxidative stress, inflammation, poor nutritional status, dyslipidemia, hypertension, erythrocyte fragmentation, and alteration of erythropoietin function 2