Red Cell Distribution Width (RDW) is a crucial component of a complete blood count (CBC) test. RDW helps guide the practitioner in dealing with some types of anemia. Anemia affects the global population by 27%. Understanding RDW results provides valuable insights for patients and practitioners, identifying underlying health issues and guiding appropriate medical interventions.
The purpose of the article is to investigate this individual marker in depth, help guide the practitioner and patient to a deeper understanding, and open the door to deeper and longer-lasting healing.
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What is RDW in a Blood Test?
RDW stands for Red Blood Cell Distribution Width, a measure of the variation in size or volume of red blood cells (RBCs). It assesses the uniformity of RBCs in a blood sample. A higher RDW value indicates greater variation in RBC size, which can signal various health conditions.
Normal RDW Range
The normal RDW range typically falls between 12% and 15%. However, this range can vary slightly depending on the laboratory and the specific method used. There are two main types of RDW measurements:
- RDW-CV (Coefficient of Variation): Expressed as a percentage, it reflects the ratio of the standard deviation of RBC size to the mean cell volume (MCV). A ratio is a part of the whole. Therefore, the standard deviation is the number of cells, mostly around a particular cell size, to the mean or average size (Fischbach & Dunning, 2009, #104).
- RDW-SD (Standard Deviation): Measured in femtoliters (fL), it represents the actual difference in RBC sizes (Rupa Health Reference Guide, n.d.).
Understanding these measurements is essential for accurate diagnosis and treatment planning. Significantly elevated RDW values require further investigation to identify and treat underlying health issues.
High RDW Meaning
A high RDW, or anisocytosis, indicates greater than normal variation in RBC size. Further testing is often necessary to determine the cause.
Common Causes of High RDW
- Anemia: High RDW is commonly associated with various types of anemia, including:
- Iron Deficiency Anemia is the most prevalent form of anemia. It is caused by insufficient iron intake or chronic blood loss, leading to smaller-than-normal RBCs.
- Vitamin B12 Deficiency: Results from inadequate vitamin B12 absorption, leading to larger-than-normal RBCs. A form of B12 deficiency is pernicious anemia.
- Folate Deficiency: Similar to vitamin B12 deficiency, causing abnormal RBC production and size variation.
- Hemoglobinopathies: Conditions like Sickle Cell or C disease and Beta-Thalassemia, where RBC fragmentation increases RDW variation.
- Hemolytic anemias: Fragmentation of RBCs will increase the RDW (Anemia - Hemolytic Anemia, 2022).
- Post-hemorrhagic anemias: Bone marrow response to bleeding releases premature RBCs (reticulocytes) into circulation, larger than typical RBCs (Kirkman & Riley, Jr., 1959).
- Chronic liver disease: Chronic liver disease, which can lead to cirrhosis or fibrosis, affects protein production in the liver, and this is potentially reflected in RDW results.
- Recent blood transfusion: Recent blood transfusions can increase RDW due to variations between donor and recipient blood cell size, oxidative damage to donor’s blood cells during storage, and/or due to release of cytokines, which are the communications of the immune system signaling a problem (Fischbach & Dunning, 2009).
- Chronic Diseases: Chronic conditions like cardiovascular diseases and diabetes can lead to elevated RDW levels. These diseases often cause chronic inflammation and oxidative stress, affecting RBC production and lifespan (Pagana & Pagana, 2010, p 455 - 462).
- Inflammatory and Autoimmune Disorders: Conditions like rheumatoid arthritis and lupus can elevate RDW due to chronic inflammation and immune system dysfunction, affecting the bone marrow's ability to produce uniformly sized RBCs.
- Bone Marrow Disorders: High RDW can indicate bone marrow disorders such as myelodysplastic syndromes, which disrupt normal RBC production and lead to increased size variation (Fischbach & Dunning, 2009) (Pagana & Pagana, 2010 p 455 - 462).
- Cancer: Certain cancers, particularly those affecting the bone marrow, like leukemia, lymphoma, and multiple myeloma, are associated with high RDW levels (Fischbach & Dunning, 2009) (Pagana & Pagana, 2010 p 455 - 462).
Symptoms Associated with High RDW
High RDW is often accompanied by symptoms such as:
- Fatigue: A common symptom that may be due to inadequate or an inability for the red blood cells to either carry oxygen or transport oxygen to the tissues.
- Weakness: Resulting from decreased oxygen supply to muscles and tissues.
- Pallor: Pale skin caused by reduced RBC count or hemoglobin levels.
- Dizziness: Lightheadedness or spinning due to oxygen not being delivered adequately to the tissues.
Clinical Implications
High RDW can indicate underlying health issues requiring further investigation. Practitioners should consider RDW with other CBC parameters for an accurate diagnosis.
Lab Tests and Additional Testing
A CBC with differential is the first test to explore, as it provides many insights into the patient's health and well-being.
RBC Count
A high RBC count and a high RDW can indicate polycythemia, a condition characterized by excessive RBC production (Fischbach & Dunning, 2009). This requires further diagnostic tests to determine the underlying cause.
Conversely, a low RBC count, hemoglobin, or hematocrit with an increased RDW indicates iron-deficiency anemia.
Hemoglobin and Hematocrit
RDW, when evaluated with hemoglobin and hematocrit levels, provides a comprehensive view of a patient's hematologic health. A high RDW with:
- A low hemoglobin and/or hematocrit often points toward anemia
- A high hemoglobin/hematocrit may indicate other disorders such as polycythemia.
MCV (Mean Corpuscular Volume)
The combination of RDW and MCV helps diagnose specific types of anemia: A high RDW with:
- A low MCV: Suggests iron deficiency anemia or thalassemia.
- A high MCV: Indicates vitamin B12 or folate deficiency anemia.
Biomarkers Related to High RDW
- The reticulocyte count is an important test to help distinguish chronic disease states from hemolytic anemia and/or acute blood loss. (Fischbach & Dunning, 2009) (Reticulocyte Count, n.d.).
- Iron studies include serum iron, ferritin, and TIBC to diagnose iron deficiency. If Iron or Ferritin (the body’s storage of iron) is low the person may suffer from iron deficiency, especially if they are a menstruating female (Iron + Total Iron Binding Capacity by Access Labcorp Draw, n.d.) (Fischbach & Dunning, 2009) (Pagana & Pagana, 2010 p 455 - 462).
- Vitamin B12 and folate (these must be measured together because they present with similar patterns) will differentiate one deficiency from the other and possibly help to distinguish if it is an absorption condition such as Pernicious anemia (Vitamin B12 & Folate by Access Med Labs, n.d.) (Pagana & Pagana, 2010, p 455 - 462) (Cloyd, 2023) (Cloyd, 2023).
- Liver Function tests will be necessary to determine if the issue is with production or protein (all proteins are made by the liver) (Fischbach & Dunning, 2009, #)(Pagana & Pagana, 2010 p 455 - 462) (Sweetnich, 2023).
Finally, if testing is inconclusive, a referral to a hematologist is vital to the patient, so they may be seen and if necessary, preform a bone marrow biopsy or explore cancer testing (Percival, 2017).
Interpretation of Results
Diagnostic Approach
When RDW is elevated, doctors assess the patient’s medical and family history, dietary habits, and symptoms, perform a physical exam (which might reveal shortness of breath, balance, pallor/paleness, and weakness), and conduct relevant tests. All of this together provides a picture of the patient's life that provides an understanding of how they got there. Once one understands the how, one may implement the what not part of treatment.
Management and Treatment Options
Treatment depends on the underlying cause of high RDW:
- Nutritional Supplementation: Improved eating habits and diets, digestion, and absorption of nutrients through the gut/intestinal wall so that the nutrients may be best utilized and providing iron, vitamin B12, or folate supplements if required/needed.
- Managing Chronic Diseases: Lifestyle modification is the driver of most chronic diseases. What got you here likely won’t get you out of here. Supplements, herbs, and medication for conditions like diabetes or cardiovascular diseases may be needed to help the patient move from pathology to feeling better so that they can adopt more healthy habits and keep the momentum as they travel the continuum of health.
- Treating Inflammatory Disorders: Anti-inflammatory lifestyle interventions (including diet, exercise, and spiritual practices) and adding in supplements (like fish oil), herbs, medications, or immunosuppressants for autoimmune conditions will address inflammation that prevents the body from healing.
Additional Tests: Other functional testing may be assessed to determine the causative reasons for the diseased state. These tests include small intestinal overgrowth (SIBO) testing, stool analysis, nutritional evaluations, oxidative stress testing, and hormones. These are not direct causes but more indirect causes that inflict pathology on the system, bringing it out of balance or homeostasis.
Monitoring and Follow-up
Regularly monitoring RDW and other blood parameters is essential for effectively managing the underlying condition. Follow-up blood tests help track treatment progress and adjust interventions as needed.
Patient Communication and Education
It is essential to assure patients that further testing is necessary to determine the right course of action, and is called due diligence. Emphasize the importance of accurate diagnosis through testing. Clear and honest communication can ease patient's worries and help them understand the significance of RDW results.
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Key Takeaways
- Understand and Interpret RDW results to identify and diagnose various underlying health conditions that guide appropriate medical interventions.
- High RDW can indicate anemia, chronic diseases, nutritional deficiencies, inflammatory disorders, bone marrow disorders, or cancer.
- Common symptoms include shortness of breath, balance issues, pallor/paleness, and weakness.
- First, the various anemias should be ruled out, and treatment should be provided. If unresolved, consider further functional testing such as SIBO if a nutritional deficiency.
- Consulting healthcare providers for personalized interpretation and advice is essential for accurate diagnosis and effective treatment.
- Be proactive about your health with regular check-ups to maintain your overall well-being. Remember, it is better to know than ignore. Knowing allows one to act, and not knowing doesn’t disappear the condition or pathology.
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