Management of Elevated Red Cell Distribution Width (RDW)
For patients with elevated RDW (>14.0%), a systematic diagnostic approach should be implemented to identify the underlying cause, followed by targeted treatment of that specific etiology. 1, 2
Diagnostic Approach
- Elevated RDW should always be interpreted alongside other hematologic parameters including hemoglobin, MCV, and other red cell indices 1
- Minimum workup for elevated RDW should include:
- Complete blood count with MCV
- Reticulocyte count
- Serum ferritin
- Transferrin saturation
- CRP (to assess for inflammation) 2
Interpretation Based on MCV
- Microcytic anemia (low MCV) with high RDW: Strongly suggests iron deficiency anemia 1, 2
- Normocytic anemia (normal MCV) with high RDW: May indicate early iron deficiency, vitamin B12 or folate deficiency, or hemolysis 1
- Macrocytic anemia (high MCV) with high RDW: Consider vitamin B12 or folate deficiency 1
Management Based on Underlying Cause
Iron Deficiency Anemia
- Confirm diagnosis with serum ferritin (<30 μg/L without inflammation, <100 μg/L with inflammation) 2
- Initiate iron supplementation (oral or intravenous) 2
- Investigate potential sources of blood loss, particularly gastrointestinal causes 2
- For adult men and post-menopausal women, both upper and lower gastrointestinal endoscopy should be performed to exclude malignancy 2
Vitamin Deficiencies
- For B12 deficiency: Administer vitamin B12 supplementation 1
- For folate deficiency: Provide folate supplementation 1
Inflammatory Conditions
- Address the underlying inflammatory disorder 1
- Monitor RDW as a potential marker of treatment response 2
Hemoglobinopathies
- If thalassemia is suspected (microcytosis with normal or mildly elevated RDW), appropriate hemoglobin electrophoresis should be performed 1, 3
- Sickle cell disorders typically present with markedly elevated RDW and require specific management 3, 4
Additional Considerations
- Vitamin D deficiency has been associated with elevated RDW in community-dwelling adults, suggesting that vitamin D status assessment may be warranted in patients with unexplained elevated RDW 5
- Elevated RDW has been associated with increased mortality in various conditions including cardiovascular disease, and may reflect neurohumoral activation as evidenced by its correlation with BNP levels 6, 7
Common Pitfalls to Avoid
- Assuming iron deficiency based solely on microcytosis without checking RDW 2
- Failing to investigate for gastrointestinal malignancy in adult men and post-menopausal women with iron deficiency anemia 2
- Overlooking the possibility of combined deficiencies (e.g., iron and B12), which may result in a normal MCV despite abnormal RDW 2
- Attributing microcytosis to thalassemia in certain ethnic groups without laboratory confirmation 2
- Neglecting to interpret RDW in the context of other hematologic parameters 1