Updated: Apr 12, 2022
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The RDW is an important biomarker for vascular health and inflammation.
Here is an excerpt from my upcoming book that explains the RDW biomarker in great detail.
Red Blood Cell Distribution Width (RDW)
RDW is more complicated to interpret compared to WBC because it is less specific as explain earlier in this chapter. Red cell distribution width‐coefficient of variation (RDW—CV) is a routine component of the complete blood count, automatically generated by most hematology analyzers at no extra cost. It is a very inexpensive test. RDW is a quantitative estimation of the heterogeneity of volume of red blood cells (RBCs), commonly known as anisocytosis. Elevated RDW can result from an increase in RBC volume variance and/or a reduction in mean corpuscular volume (MCV). However, the RDW value also reveals inflammation to those who understand the various ranges associated with the RDW value.
The diagnosis of anisocytosis means that your red blood cells are of mixed sizes. Normally, red blood cells should be about the same size – in the range of 11.5 – 12.5 percent. Highly elevated RDW values are classically associated with anemia. WebMD answers the question, “what is the RDW?”[i]
“RDW stands for the red blood cell distribution width. This is a standard reported measure on a complete blood count (CBC) lab test. It measures the variability in red blood cell size.
In the normal state, red blood cells are continually being produced and removed from the blood at a steady rate. The young, immature red blood cells are larger than mature red blood cells. There are predictable proportions of large and small red blood cells, which can be plotted on a graph as the normal values.
In certain forms of anemia, the RDW may be higher than normal because there are more immature or abnormal red blood cells skewing the statistical range of values.
The RDW result is nonspecific. If a doctor suspects an unusual form of anemia, there are more sophisticated tests that can make the diagnosis.”
WebMD used “the kiss of death” term for RDW – “nonspecific.” Nonspecific means the marker goes up in many conditions. In standard-of-care lingo it means doctors do not have a drug specifically made to treat elevated RDW. This creates a problem for medical providers as there is no expedient way to lower RDW. They prefer convenient diagnoses like “cholesterol” so they can quickly prescribe a pill and send you on your way, often to poorer health. Sixty percent of Americans have at least one chronic condition for a reason.
Nonspecific, however, is what chronic diseases are. Governments, societies, consensus groups, and insurance actuaries come up with categories of disease. The chapter on immunity shows that are only 5 types of white blood cells defending our health – yet there are 77,000 named diseases in the 2020 coding book ICD-10. Why do we not have 77,000 different types of immune responses? Keep in mind that in 1979, ICD-9 was established with just 14,000 diagnostic codes. Since 1979, have 63,000 new disease-fighting mechanisms been acquired by humans, or have there been 63,000 new drugs marketed? In fact, in 2022 there are over 20,000 drugs approved for marketing by the FDA. The point is, almost every chronic disease overlap in terms of immune response. Who is right, ICD-10 or immunity?
Markers that are non-specific are a blessing, especially if there are ways to improve them. Imagine lowing your RDW value and, at the same time, lower your risk for heart disease, cancer, diabetes, and Alzheimer’s. Who would be against that?
Upon careful review of the science behind the “life and times” of red blood cells, four health ranges emerge for this biomarker: low, optimal, inflammation, and anemia. The inflammation range is not considered in the standard of care and current references ranges for RDW consider the inflammatory range “normal,” Figure 7.
RDW is a profound indicator of your current health risk and future prognosis. It is an indication of vessel health. In the inflammation zone, the inflammatory marker C reactive protein (CRP) is usually elevated above the scientific normal value by approximately the same amount as the RDW. CRP is a protein made by the liver and sent into the bloodstream in response to inflammation. The test pair is quite indicative of the health of your capillaries where most of your physiological activity is oc