Platelet Distribution Width (PDW) Blood Test: Interpretation, Management, and Related Disorders

Understanding your health doesn’t always require complicated scans or expensive procedures—sometimes, a simple blood test holds powerful clues. One such test is the Platelet Distribution Width (PDW) blood test.
Often overlooked, the PDW test can reveal vital insights into how your platelets behave, signalling everything from nutrient deficiencies to serious conditions like blood disorders, tumours, or heart disease.
In this blog, we explain what PDW means, why it matters, and how regular monitoring can be a game-changer for early detection and personalised care.

Key Highlights

• PDW measures the variability in platelet size, which gives information about platelet activation and function.
• High PDW can indicate conditions like tumours, blood disorders, iron deficiency, and cardiovascular or respiratory diseases.
• The key to managing high PDW is tackling the root cause – this could involve treating the primary disease, addressing iron deficiency or initiating antiplatelet therapy.
• Regular monitoring of your PDW and other platelet indices can provide crucial insights into your health condition.

What is PDW?

Platelets are small blood cells produced by megakaryocytes in the bone marrow. They play a crucial role in forming clots to stop bleeding. Platelet Distribution Width (PDW) measures how much the size of these platelets varies in your blood.

The typical PDW range—measured by automated haematology analysers—is between 15.1% and 17.9%. However, levels can be influenced by various factors such as platelet activation disorders, iron deficiency anaemia, age, sex, and genetic traits.

A high PDW indicates greater variability in platelet size, often due to larger or more reactive platelets in circulation. These activated platelets may signal an ongoing response to injury, inflammation, or underlying disease.

Understanding your PDW levels can offer valuable insights into your health and help guide early intervention. Regular check-ups with your doctor can ensure any abnormalities are addressed promptly.

Did you know! Beyond clinical diagnostics, PDW also plays a role in forensic science. Forensic pathologists use PDW readings to help determine causes of death—such as distinguishing sudden cardiac death from other causes—highlighting its fascinating application at the intersection of medicine and law.

How is the PDW Blood Test Performed?

The PDW blood test is a crucial component of routine medical check-ups. This test helps measure the variability in the size of platelets in our blood, giving us insight into the range of sizes in which platelets come. 

The PDW blood test is usually performed as part of a larger evaluation and is often included in a Complete Blood Count (CBC) or a platelet function assessment.

Here’s a simple step-by-step explanation of how the PDW blood test is done:

1. A trained healthcare professional uses a small needle to collect a blood sample, typically from a vein in your arm. The process involves minimal discomfort and lasts just a few minutes.
2. Once the sample is collected, it is carefully stored in a tube.
3. The tube is then sent to a laboratory and analysed using an automated haematology analyser.
4. This machine calculates the PDW value by examining the size variation of platelets in the blood sample.
5. After the analysis, your doctor will receive and discuss the results with you.

Normal PDW Range and Interpretation

The standard reference interval for PDW typically falls between 9.0% and 17.0% for adults. A PDW value below 9% signifies more uniform platelet size, which usually suggests normal platelet function. However, a PDW value above 17% indicates a greater variability in platelet size, which can be a sign of increased platelet activation.

It’s important to note that elevated PDW values have been associated with several health concerns. Therefore, it is important to monitor PDW and other platelet indices regularly.

Understanding High PDW

A high PDW, particularly values above 16.7%, may indicate several health concerns. Here’s what an elevated PDW may suggest:

• Greater variability in platelet size suggests increased platelet activation. There are also more severe clinical profiles, that is, more severe symptoms and worse outcomes, and higher mortality rates in patients with conditions like cardiovascular disease, diabetes, or chronic inflammatory diseases.
• Increased risk of abnormal blood clotting (thrombosis) and complications due to bleeding.
• Early signs of preterm birth in pregnant women.
• Progression and prognosis of long-term diseases like cancer, bleeding disorders, and thyroid disorders.

Managing High Platelet Distribution Width

Now that we understand what high PDW might indicate, let’s consider how one might manage it.

The key to managing high PDW is identifying and addressing the underlying cause. Here are some strategies that doctors might recommend:

1. Undergoing treatment for the primary disease causing platelet activation, such as cancer, cardiovascular disease, or respiratory disorders.
2. Managing iron deficiency anaemia through diet or supplements.
3. Antiplatelet therapy should be considered if high PDW is due to abnormal platelet function.
4. Regular monitoring of PDW along with other platelet indices to track disease progression and treatment response.

While these steps can help manage high PDW, remember that they should be guided by your doctor’s advice.

Platelet-Related Blood Disorders

Platelet disorders often involve a decrease in the number of platelets, a condition commonly termed thrombocytopenia, or a problem with their function. These functional disorders may be inherited (although rare) or acquired (which is more common).

The major platelet-related blood disorders include:

• Immune Thrombocytopenia (ITP) is an autoimmune disorder in which the body mistakenly attacks its own platelets, leading to a low platelet count.
• Thrombotic Thrombocytopenic Purpura (TTP): A rare disorder characterised by low platelet counts and clots that develop in small blood vessels.
• Von Willebrand Disease: This is the most common inherited bleeding disorder. It is caused by a deficiency or abnormality of the von Willebrand factor, which is required for proper platelet adhesion.
• Glanzmann Thrombasthenia is another rare inherited disorder where the platelets fail to aggregate properly because of dysfunction.

Diagnosis and Management of Platelet Disorders

Diagnosing platelet disorders involves various tests, including blood tests, genetic tests, and, in some instances, even bone marrow examination. The key tests typically include the following:

• CBC is used to check the number of platelets.
• Platelet function tests assess the effectiveness of your platelets.
• Genetic testing, which is used primarily for diagnosing inherited disorders

The treatment plan varies depending on the specific disorder and its severity. 

Some standard treatment options include:

• Medications to boost platelet production or prevent their destruction
• Platelet transfusions, especially in cases of severe bleeding
• Addressing the underlying cause, such as autoimmune disorders
• Avoidance of certain medications that affect platelets, like aspirin

Complications of Platelet Disorders

Platelet disorders can lead to various complications, such as:

• Severe or prolonged bleeding, particularly after injuries or surgical procedures
• Depleted iron levels due to chronic bleeding
• Potential damage to organs from blood clots in disorders like TTP

Expert Quote:

“ The PDW test is useful in helping us detect early signs of platelet-related disorders and tailor treatment accordingly. However, since its value range varies in different laboratories, it cannot be a reliable marker. Always consult your doctor for further evaluation.”

– Dr. Sachin Singh

Takeaway

The PDW (Platelet Distribution Width) blood test is valuable in assessing your overall health. It measures the variation in platelet size, which can indicate potential underlying conditions such as tumours, blood disorders, or cardiovascular diseases. 

Elevated PDW levels often point to further investigation and may require treatment of root causes like iron deficiency or chronic illness. Regular monitoring of PDW, along with other platelet indices, enables healthcare providers to detect abnormalities early and offer personalised, effective care tailored to each patient’s needs.

Frequently Asked Questions (FAQs)

References

• Tzur, I., Barchel, D., Izhakian, S., Swarka, M., Garach-Jehoshua, O., Krutkina, E., Plotnikov, G., & Gorelik, O. (2019). Platelet distribution width: a novel prognostic marker in an internal medicine ward. Journal of Community Hospital Internal Medicine Perspectives, 9(6), 464–470. https://doi.org/10.1080/20009666.2019.1688095
• Smith, S. (2023, October 23). Understanding your blood test results | Roswell Park Comprehensive Cancer Center – Buffalo, NY. Www.roswellpark.org. https://www.roswellpark.org/cancertalk/202310/understanding-your-blood-test-results