Low Red Blood Cell Distribution Width and Autoimmune Diseases

In this article, we will take a close look at the relationship between low red blood cell distribution width (RDW) and autoimmune diseases. We will delve into the significance of RDW, its relevance in health and disease, and its potential role as an index in assessing the activity of autoimmune conditions.
Frederika Malichová

Frederika Malichová

Neuroscientist at the University Of Cambridge.

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​Low Red Blood Cell Distribution Width and Autoimmune Diseases

Research indicates a correlation between low red blood cell distribution width (RDW) and autoimmune diseases. Lower RDW values may be indicative of certain autoimmune conditions. However, more comprehensive studies are needed to fully understand this relationship. Always consult a healthcare professional for medical advice.

What is red cell distribution width?

Red cell distribution width (RDW) is a measure of the variation in size and volume of your red blood cells. Usually, it is a part of the complete blood count (CBC) test which evaluates the cells that circulate in your blood.

It provides additional information in the context of other parameters like hemoglobin or mean corpuscular volume. High RDW values may indicate a nutrient deficiency, anemia, or other hidden conditions [1].

Any deviation from the normal range in red blood cell width can signal a potential problem with a bodily function that may affect oxygen delivery to some parts of your body [1]

Red blood cells are important for carrying oxygen from the lungs into all the body parts [1].

The standard size of normal red blood cells is 6-8 micrometers in diameter. When there is a change in the RDW, it means that there is a large range of sizes among your red blood cells.

For example, if your red blood cells are generally small, but you also have a lot of very small cells, your RDW will be elevated [1].

When do we see low red cell distribution width?

Low Red Cell Distribution Width (RDW) is typically observed in healthy individuals, as it indicates a uniform size of red blood cells. It does not indicate any health problems.

However, for instance, in acute coronary syndrome (ACS), a low RDW is associated with a lower short-term mortality risk. In fact, one study found that short-term cardiovascular mortality was 10,2% in the low RDW group, compared to 47% in the high RDW group [2]. Another study suggested that low RDW in acute coronary syndrome is associated with a lower risk for major adverse cardiovascular events (MACEs) after an ACS [3].

Even in patients with iron deficiency anemia low RDW can be seen in the early stages of the condition indicating good health. This can be detected even before other tests become positive. Since RDW is a measure of the variation in red blood cell size, the variation is not significant in the early stages of the condition [4, 5].

Although low RDW is generally a good sign, it does not rule out certain health conditions straight away and should be interpreted in the context of other clinical and laboratory findings.

What are autoimmune diseases?

Autoimmune diseases are conditions in which the immune system attacks its body’s cells leading to inflammation and damage.

These conditions are quite prevalent and affect more than 20% of the population [6].

There are over 80 different autoimmune diseases that can affect various parts of the body [7, 8].

This is not a natural immune response, as the immune system should protect its own body. In autoimmune diseases, the immune system fails to distinguish between foreign invaders and the body’s cells. This leads to the production of autoantibodies that attack healthy tissues. However, such reactions can be caused by a variety of genetic predispositions and environmental triggers [9, 10, 11].

Autoimmune diseases can be either organ-specific, where they affect a particular tissue. An example of organ-specific autoimmune disease is type 1 diabetes or thyroiditis [7, 10].

Further, it can be systemic with examples like systemic lupus erythematosus or rheumatoid arthritis [7, 10]

What is the relevance of red blood cell distribution width and autoimmune diseases?

According to recent studies, RDW appears to be a useful marker in assessing the severity and activity of autoimmune diseases.

For instance, in systemic lupus erythematosus (SLE) (a type of autoimmune disease), RDW has been found to correlate with disease activity [12].

Further, RDW has also been investigated in relevance to rheumatic diseases (autoimmune diseases affecting the joints and connective tissues). According to some studies RDW has the potential to be a marker for disease activity in patients suffering from these conditions. Some studies reported a significant correlation between elevated RDW and disease activity, but on the other hand, some reported inconclusive results [13].

Another example of the use of RDW is inflammatory bowel disease. Clinical studies have found that RDW might serve as a proxy to differentiate Crohn’s disease and ulcerative colitis [14].

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Frederika Malichová

Frederika Malichová

Frederika is a postgraduate researcher at the University of Cambridge, where she investigates new biomarkers for Frontotemporal Dementia and other tauopathies. Her research has been published at prestigious conferences such as the Alzheimer’s Association International Conference 2023. She obtained her BSc in Biomedical Sciences from UCL, where she worked closely with the UK Dementia Research Institute.