The Red Cell Distribution Width (RDW) Blood Test measures the degree of variability in the volume and size of red blood cells. Red blood cells are required to transport oxygen from the lungs to every region of the body. Red blood cell width or volume readings that fall outside of the usual range suggest a potential problem with biological function, which might then influence how well oxygen reaches different sections of the body. One may still have a normal RDW, nevertheless, with several disorders. The diameter of typical red blood cells remains constant at 6 to 8 micrometres (µm). An elevated RDW is associated with a wide range of sizes.

The presence of red blood cells with a significant degree of fluctuation in size might indicate anaemia. Unhealthy red blood cells are insufficient to carry oxygen to your body's organs, which is a symptom of anaemia. The doctor might use a variety of lab tests, including an RDW test blood, to identify anaemia or other disorders.

What is an RDW Blood test?

Red blood cells' (RBCs) size variations within a blood sample are quantified by the term "red cell distribution width" (RDW). The RDW test measures the variety of RBC sizes in a blood sample. Anaemia is a disorder in which there is insufficient healthy RBCs to adequately transport oxygen to the rest of the body. To diagnose and ascertain the reason for anaemia, an RDW test is carried out in conjunction with other tests. The RDW in blood report is a component of a complete blood count (CBC), a common test used to identify and track a wide range of medical disorders.

An RDW blood test may be useful to identify disorders that may lead to anaemia, such as:

• Iron deficiency
• Kidney disease
• Liver disease
• Vitamin B12 or folate deficiency
• Heart disease
• Cancer
• Thalassemia, an inherited blood disorder

When should I get this RDW blood test?

The RDW blood test is often used for screening otherwise healthy people as well as for the evaluation of various medical disorders, including anaemia. It is also known as the RDW-SD (standard deviation test) or erythrocyte distribution width. If a patient has symptoms related to anaemia or a disease associated with anaemia, an RDW blood test can assist the doctor in making a more accurate diagnosis.

Depending on the underlying medical condition or ailment, anaemia symptoms can range from mild to severe. Mild anaemia can appear suddenly, develop gradually over time, or show no symptoms at all. The following are a few early or moderate warning signs of anaemia that might prompt a doctor to request an RDW test:

• Headaches
• Loss of appetite
• Feeling particularly weak or exhausted, especially after exercising
• Numbness or tingling in the hands and/or feet
• Irritability or a sense of agitation
• Difficulty focusing or thinking

Additional indications and symptoms of anaemia may include:

• Feeling dizzy
• Brittle nails
• Mouth ulcers
• Being out of breath even during light activities
• Unusually pale skin
• An abnormally red or possibly itchy tongue
• A desire to consume non-food items like ice, dirt, or other objects
• Slight bluishness in the whites of the eyes.

Limitations of the RDW Blood Test

While the RDW test can provide valuable information about various health conditions, it also has its limitations:

• Non-Specificity: RDW alone is not diagnostic of any specific disease or condition. It serves as a general indicator of red blood cell size variation. Additional tests and clinical evaluation are typically required to diagnose the underlying cause of abnormal RDW results.
• Limited Information: RDW does not provide a comprehensive picture of overall health. It focuses specifically on red blood cell size variation and does not assess other aspects of blood health or other body systems.
• Possible False Positives/Negatives: RDW levels can be influenced by various factors, including certain medications, recent blood transfusions, and dietary deficiencies. Additionally, normal RDW levels do not rule out the presence of certain health conditions, and abnormal RDW levels do not necessarily indicate a specific disease.
• Interpretation Challenges: Interpreting RDW results can be complex, especially in the absence of other clinical information. A high RDW may indicate several conditions, including anemia, nutritional deficiencies, chronic diseases, or bone marrow disorders, among others. Conversely, a normal RDW does not exclude these conditions.

Procedure for RDW blood test

The procedure will be the same as a standard blood collection.

• The best location to draw blood will be determined by the medical professional; typically, this is in the crook of the arm or on the back of the hand. The location where the needle will be inserted will be cleaned and sterilised.
• To restrict blood flow in the arm and make the vein easier to visualise and access, the doctor will apply an elastic band to the arm above the injection site.
• The sample will be obtained by the attending doctor. Upon the insertion of the needle, the patient may feel an instant sting or pressure. A vial containing the blood sample will be connected to the needle.
• Once enough blood has been collected, the needle will be removed, and any bleeding will be controlled by bandaging the injection site.

Uses of RDW blood test

RDW testing can assist doctors in determining the type of anaemia a patient may have if they suspect it. The RDW test often serves as a component of a CBC, a test that evaluates every element of the blood, including haemoglobin, platelets, and white blood cells. Doctors can learn more about the potential causes of anaemia via a CBC. It may be helpful in the diagnosis of several other medical conditions, such as:

• Diabetes
• Heart disease
• Liver disease
• Cancer
• Thalassemia (A genetic blood condition that lowers haemoglobin levels)

A person may require a CBC if they experience any of the following:

• Anaemia symptoms such as weakness, a pale complexion, and lightheadedness.
• A diet deficient in minerals like iron, vitamin B12, or others.
• A family history of blood diseases, such as thalassemia or sickle cell anaemia.
• Chronic conditions such as Crohn's disease, HIV, or diabetes.
• Significant bleeding after an operation or injury.

A CBC test may indicate anaemia if the results show low levels of haemoglobin or red blood cells. After that, using the RDW and other tests, doctors attempt to identify the problem.

How to prepare for the RDW blood test?

An RDW test doesn't require any extra preparation. However, if a doctor has prescribed additional blood tests along with the RDW, the patient might need to fast before the test. The doctor will inform them in advance about this and any other requirements.

What are the risks of an RDW blood test?

The RDW blood test itself is a relatively low-risk procedure, similar to other routine blood tests. Risks associated with the RDW blood test are minimal and primarily involve the standard risks associated with any blood draw. These risks may include:

• Pain or Discomfort: Some individuals may experience mild pain, discomfort, or bruising at the site where the blood is drawn. This is usually temporary and resolves quickly.
• Bleeding or Hematoma: In rare cases, excessive bleeding or the formation of a hematoma (a localized collection of blood outside blood vessels) may occur at the blood draw site. This risk is higher in individuals with bleeding disorders or those taking blood-thinning medications.
• Infection: While modern blood collection techniques and sterile equipment minimize the risk of infection, there is still a very small risk of infection at the site of blood collection. This risk is further reduced by following proper hygiene and sterilization protocols.
• Fainting or Lightheadedness: Some people may feel faint, dizzy, or lightheaded during or after the blood draw. This is usually temporary and can be minimized by lying down during the procedure and avoiding sudden movements afterwards.

Values of RDW blood test Results

The RDW in a blood report, which measures the degree of fluctuation in RBC size, is often expressed as a percentage. By comparing the RDW result to a reference range (a range of values defined by the testing facility as predicted RDW levels for a healthy individual), the RDW result can be understood.

• Normal Result: If the result is normal, it means the red blood cells are all of a similar size. A normal RDW typically falls within the range of 11.5% to 14.5%, but this value may vary depending on the lab conducting the test.
• High RDW - RDW blood high levels (red blood cell distribution width) indicate that the variation in red blood cell sizes is greater than what is considered normal. A high RDW in a blood test may indicate anaemia or an associated illness.
• Low RDW - A low RDW (less than 10.2%) in an RBC (red blood cell) blood test is often not a cause for alarm and is not specifically linked to any particular forms of anaemia.

Conclusions

High RDW levels in blood tests can result from various factors. Therefore, it is advisable to seek a comprehensive medical evaluation from a doctor before making any hasty decisions. With prompt and appropriate medical interventions, it is possible to manage RDW levels.

CARE Hospitals is the country's premier healthcare facility providing advanced laboratory services with a wide range of diagnostic tests, including the RDW test. Our lab is equipped with state-of-the-art equipment and staffed by trained professionals to ensure precise and reliable results. Whether you need the RDW test or any other diagnostic test, you can easily access it at CARE Hospitals.

FAQs

1. What does a high RDW blood level mean?

Ans. A high red blood cell volume (RDW) indicates anaemia or an underlying medical condition, as it measures the variation in red blood cell size within the blood.

2. Is high RDW blood serious?

Ans. A high RDW level may suggest anaemia or a related condition, necessitating further diagnostic tests by a doctor. Often, the doctor will compare RDW results with MCV (Mean Corpuscular Volume) results to assess the red blood cell condition.

3. What does it mean when your RDW is low?

Ans. A low RDW in blood report (less than 10.2%) indicates minimal variation in red blood cell size. One potential cause of a low RDW level is macrocytic anaemia.

4. What is the normal range for RDW SD?

Ans. The reference range for RDW blood test SD is as follows:

• RDW-SD: 39-46 fL

• RDW-CV: 11.6-14.6% in adults

5. What is a good RDW level?

Ans. A favourable RDW level typically falls between 12 and 15%, demonstrating how closely red blood cell sizes in a sample align with the normal range.