Blood tests are a fundamental aspect of modern healthcare, providing valuable insights into the body’s internal workings. They measure various components within the blood, reflecting overall health. Analyzing blood samples helps healthcare professionals detect subtle changes that may signal underlying health issues, often before symptoms appear. This supports early identification of conditions, enabling timely intervention and guiding personalized medical care.
Understanding RDW
“RDH” is a common misspelling for “RDW,” which stands for Red Cell Distribution Width. The RDW test measures the variation in the size and volume of red blood cells (erythrocytes) in a blood sample. It provides insight into the uniformity of these oxygen-transporting cells. Normally, red blood cells are relatively consistent in size, typically ranging from 6.2 to 8.2 micrometers in diameter.
The RDW is calculated as part of a complete blood count (CBC). A higher RDW indicates greater variability in red blood cell size, a condition called anisocytosis. Conversely, a lower RDW suggests red blood cells are more uniform.
Why RDW is Measured
Measuring RDW aids in diagnosing and differentiating various types of anemia. Anemia is a condition where the body lacks sufficient healthy red blood cells to carry adequate oxygen. RDW helps distinguish forms like iron deficiency anemia (smaller, varied cells) or megaloblastic anemias from vitamin B12 or folate deficiencies (larger, varied cells).
The RDW test also assists in identifying other conditions affecting red blood cell production or survival. These include chronic inflammation, liver disease, or kidney disease. An elevated RDW can be an early indicator of nutritional deficiencies, sometimes appearing before other red blood cell parameters change.
Interpreting RDW Results
A high RDW, indicating anisocytosis, means significant variation in red blood cell size. This can signal conditions like iron deficiency anemia, where the body produces a mix of smaller, irregularly shaped cells. Megaloblastic anemias, from vitamin B12 or folate deficiencies, also cause high RDW due to abnormally large red blood cells. Other conditions leading to an elevated RDW include myelodysplastic syndromes, hemolytic anemias, and certain hemoglobinopathies like sickle cell disease or beta-thalassemia.
A normal RDW indicates red blood cells are relatively uniform in size. However, a normal RDW does not exclude anemia. In some cases, such as certain types of thalassemia trait or anemia of chronic disease, red blood cells may be consistently small or normal, but their overall number or function is impaired. Therefore, RDW results are always evaluated with other complete blood count parameters, such as Mean Corpuscular Volume (MCV), Mean Corpuscular Hemoglobin (MCH), and hemoglobin levels. This comprehensive approach helps healthcare providers gain a complete picture of red blood cell health.
Next Steps for Abnormal RDW
An abnormal RDW result requires consultation with a healthcare professional for proper interpretation. Do not self-diagnose, as this test is one component of a broader assessment. The provider will consider the RDW result alongside other blood test findings, symptoms, and medical history to determine the underlying cause.
Further diagnostic tests may be necessary, such as iron studies, vitamin B12 and folate levels, or specialized tests like a bone marrow biopsy. Treatment varies by diagnosis, ranging from dietary adjustments for deficiencies to specific medical interventions. Regular monitoring through follow-up blood tests is often part of the management plan.