Red Cell Distribution Width (RDW) Lab Values

Hey everyone, Abby here with nursing.com. In this lesson we’re going to discuss red cell distribution width, you’ll see it abbreviated as RDW. This lesson will talk about normal values and clinical indications for why we take this lab and what would cause it to be increased and decreased. Let’s get started. Red cell distribution width, RDW, is measured as an indicator of the degree of size of variation of size and volume of red blood cells. This helps to aid in diagnosis of blood disorders, because for the most part, our red blood cells should be all about the same size and the same volume. When it’s not, it indicates signs and symptoms of anemia. You knew that was coming didn’t you? Whenever we talk about red blood cells, we might be talking about anemia. Now, some clinical indications for drawing this lab, the red cell distribution width, would be if someone has signs and symptoms of anemia, or a family history of thalassemia or sickle cell, these of course being disorders of the red blood cells. They could also have chronic illness, be nutrient deficient or have long term infection. This is all going to have an impact on how red blood cells are produced from the bone marrow. It could also be indicated in the case of excessive blood loss. 

Normal therapeutic values are between 11.5 and 14.5%. This would indicate a small, uniform population of RBCs. So, they’re all going to be about the same. Now this is going to be taken as part of a CBC in a lavender tube as you can see here in this picture. What would cause lab values to be increased?  Well, a condition that means that there’s a high variation in size in red blood cells is an isocytosis and anemias, of course, because again, this could be, you know, microcytic, they could be macrocytic, or meaning that they’re large in size or they’re really small in size. And, it could also be increased in major organ disease again, because there’s so much that goes into the health of the bone marrow and its ability to produce blood cell components.

Now, some linchpins for this lesson. The RDW or the red cell distribution width is a measurement of the size and volume of RBCs and the variation within that sample, very important, the variation. Now, 11.5 to 14.5% indicates that we have small uniform red blood cells. They’re fitting great through the tiny capillaries and carrying around a bunch of oxygen. An increased value means that there’s high variation in size. So, some are tiny, some are little, and that mean value is indicating that there could be a problem. Either it’s a major organ disease, or it could be deficiency of nutrients. Now, this lab is not used on its own or in isolation to diagnose any type of condition; it’s actually usually associated with other, uh, lab values so that we can really measure if there’s a hematologic disorder. 

Now, you all did great on this lesson and this wraps it up. We love you guys, now go out and be your best self today, and as always happy nursing!

References:

• https://www.uptodate.com/contents/evaluation-of-the-peripheral-blood-smear?search=Anisocytosis%203&source=search_result&selectedTitle=1~15&usage_type=default&display_rank=1
• https://www.uptodate.com/contents/microcytosis-microcytic-anemia?search=Anisocytosis%203&source=search_result&selectedTitle=2~15&usage_type=default&display_rank=2
• http://uptodate.com/contents/automated-hematology-instrumentation?search=rdw%20lab%20value&source=search_result&selectedTitle=1~150&usage_type=default&display_rank=1#H5
• https://www.healthline.com/health/rdw-blood-test#results
• https://medlineplus.gov/lab-tests/rdw-red-cell-distribution-width/