From the Guidelines
Elevated Red Cell Distribution Width (RDW) is primarily caused by iron deficiency anemia, vitamin B12 or folate deficiency, and other conditions that lead to variation in red blood cell size, as indicated by recent studies 1. The causes of an elevated RDW can be multifactorial, but the most common causes include:
- Iron deficiency anemia, where the body produces smaller red cells alongside normal-sized ones
- Vitamin B12 or folate deficiency, leading to larger red cells mixed with normal cells
- Hemolytic anemia, where the destruction of red cells triggers production of new cells of varying sizes
- Recent blood transfusions
- Certain medications, liver disease, alcoholism, myelodysplastic syndrome, and chronic inflammatory conditions
- Other conditions like sickle cell disease and thalassemia can also cause RDW elevation
According to the European Consensus on the diagnosis and management of iron deficiency and anaemia in inflammatory bowel diseases 1, a wide size range of red cells, indicated by a high RDW, can help in diagnosing iron deficiency, especially in situations where microcytosis and macrocytosis co-exist. The minimum workup for anaemia should include red blood cell indices such as RDW and mean corpuscular volume (MCV), reticulocyte count, differential blood cell count, serum ferritin, transferrin saturation, and CRP concentration 1. Further testing, including complete blood count, iron studies, vitamin levels, and sometimes bone marrow examination, may be necessary to determine the underlying cause of a high RDW. Treatment depends on addressing the specific underlying condition rather than treating the RDW value itself, and caution should be exercised when administering iron supplementation to patients with destabilized erythropoiesis 1.
From the Research
Causes of Elevated Red Cell Distribution Width (RDW)
- Iron deficiency anemia: Increased RDW is a sensitive indicator of iron deficiency anemia 2, 3, 4
- Folate deficiency: Elevated RDW can be an indicator of folate deficiency, especially in patients with chronic renal insufficiency or those who are hyporesponsive to rHuEPO treatment 2, 5, 4
- Vitamin B12 deficiency: Although not always consistent, high RDW values can be associated with vitamin B12 deficiency, particularly in patients with pernicious anemia 2, 6
- Hemolytic anemia: Increased RDW can be a feature of hemolytic anemia, indicating a shortened lifespan of red blood cells 3
- Ineffective erythropoiesis: Elevated RDW can be a sign of ineffective erythropoiesis, which can occur in various diseases, including myelodysplastic syndromes and other bone marrow disorders 3
- Chronic inflammation and oxidative stress: These conditions can also affect RDW, leading to increased values 3
- Other non-anemic pathological conditions: Elevated RDW can be prevalent in various non-anemic diseases, making it a valuable tool for diagnosis and monitoring 3