From the Guidelines
An elevated Red Cell Distribution Width (RDW) is a significant indicator of underlying conditions affecting red blood cell production or lifespan, and prompt evaluation by a healthcare provider is essential to determine the cause and appropriate treatment. This finding often suggests an underlying condition such as iron deficiency anemia, vitamin B12 or folate deficiency, recent blood loss, hemolytic anemia, or certain chronic diseases like liver or kidney disease 1. According to the European consensus on the diagnosis and management of iron deficiency and anaemia in inflammatory bowel diseases, a wide size range of red cells (high RDW) can help identify iron deficiency, especially in situations where microcytosis and macrocytosis co-exist 1.
Key Considerations
- The most common forms of anaemia in inflammatory bowel diseases are iron deficiency anaemia, anaemia of chronic disease, and a combination of both 1.
- Vitamin B12 or folate deficiency, haemolytic anaemia, and drug-induced anaemia are less prevalent forms, but should also be considered 1.
- Anaemia should be investigated with red cell distribution width (RDW), mean corpuscular volume (MCV), reticulocyte count, full blood count (FBC), ferritin, transferrin saturation, and CRP levels 1.
Recommendations
- If you have an elevated RDW, you should consult with your healthcare provider for further evaluation, which typically includes additional blood tests such as a complete blood count, iron studies, vitamin B12 and folate levels 1.
- Treatment depends entirely on the underlying cause, and may include iron supplements (typically ferrous sulfate 325mg daily) for iron deficiency, vitamin B12 injections (1000mcg monthly) or supplements for B12 deficiency, or addressing any primary condition affecting your red blood cells.
- While waiting for your appointment, maintain a balanced diet rich in iron (red meat, beans, leafy greens) and B vitamins (eggs, dairy, meat) 1.
From the Research
Elevated RDW: Causes and Associations
- Elevated Red Cell Distribution Width (RDW) is associated with various health conditions, including anaemia, cardiovascular diseases, and respiratory failure 2, 3.
- RDW is a measure of the variation in red blood cell size, and an elevated RDW indicates a larger variation in cell size, which can be a sign of underlying health issues 3.
- Studies have shown that elevated RDW is associated with decreased ventilator-free days in critically ill patients 2 and increased mortality in patients with cardiovascular diseases 3.
Relationship with Anaemia and Nutritional Deficiencies
- Anaemia, characterized by low haemoglobin concentration, can be caused by nutritional deficiencies, including iron, vitamin B12, and folate deficiencies 4.
- Elevated RDW can be a sign of iron deficiency anaemia, and treatment with iron can increase serum vitamin B12 and folate levels 5.
- Combined cobalamin and iron deficiency anaemia can be diagnosed using a model based on age and homocysteine assessment, and clinicians should be aware of the overlap between iron deficiency anaemia and cobalamin deficiency 6.
Clinical Implications
- Elevated RDW can be a useful indicator of patient fragility and vulnerability to adverse outcomes, and clinicians should consider it as part of a comprehensive assessment of traditional and non-traditional risk factors 3.
- Further studies are needed to validate the association between RDW and clinical outcomes and to understand the physiologic processes that lead to elevated RDW in patients with respiratory failure 2.