Understanding Mean Platelet Volume (MPV)

Mean platelet volume (MPV) is a measure of the average size of your platelets, a type of blood cell that helps prevent bleeding. MPV is particularly important in determining the cause of thrombocytopenia (a low platelet count) or thrombocytosis (a high platelet count), and it can be a useful diagnostic tool even if your platelet count is normal.

Your MPV may also increase or decrease with some conditions such as heart disease, lupus, thyroid disease, and infections.

Platelets, also referred to as thrombocytes, are the cells responsible for forming blood clots to slow down blood loss, prevent infection, and promote healing. When an injury occurs, platelets aggregate to plug the wound and send hormone signals through the blood to attract protein clotting factors, which assist in repairing the injury.

Platelets are produced in the bone marrow by megakaryocytes, which are large precursor cells. The platelets themselves, which are released into the bloodstream from the bone marrow, are actually pieces of the megakaryocytes. Usually, younger platelets are larger in size than older platelets, and MPV is often considered a reflection of the average age of your platelets.

Mean platelet volume is measured as part of your complete blood count (CBC), a blood test used in health screening and for monitoring many health conditions. To obtain an MPV value, your blood is drawn into a purple top tube that contains an anticoagulant so the blood won't clot and, consequently, render an abnormal result for both the platelet count and MPV.

Your CBC includes your total platelet count as well as your platelet indices, such as MPV and platelet distribution width (PDW)—an indication of the variation in the width of your platelets. These indices are details about your platelets that provide a fuller description of what your actual platelets look like. In fact, even if you have a normal platelet count, abnormal indices may alert your doctor to a problem.

Ordinarily, platelet levels around 50,000 are associated with bruising. A platelet level below 20,000 can predispose you to life-threatening bleeding.

When the MPV value is high, the lab will usually check it with a blood smear. The technologist will stain a slide containing a sample of your blood and look at it under the microscope to see if the platelets are clumping together or if you actually have giant platelets.

A high MPV is usually a sign that there are more young platelets circulating in your bloodstream. After blood loss due to trauma or a procedure such as major surgery, your body consumes platelets to repair lacerations and stop the blood loss. In response, your bone marrow produces more megakaryocytes, which become young, large platelets, and your MPV rises.

You may have a high MPV with a low, normal, or high platelet count, and looking at these results together helps provide a diagnosis.

A high MPV with the following platelet counts can suggest associated conditions:

• A low platelet count along with high MPV occurs when platelets are destroyed, usually by antibodies, an infection, or toxins. For example, idiopathic thrombocytopenic purpura (ITP) is a platelet deficiency caused by the destruction of platelets without a known cause.
• A high platelet count along with high MPV can occur when the bone marrow produces too many platelets, typically due to a genetic mutation or cancer.
• A normal platelet count along with high MPV suggests conditions such as hyperthyroidism or chronic myelogenous leukemia (CML)—a type of cancer.

Conditions that may be associated with an elevated MPV and variable platelet counts include:

• Non-alcoholic liver disease
• Genetic abnormalities in platelets
• Bernard-Soulier Disease (giant platelet syndrome)
• Bone marrow stimulating drugs, such as erythropoietin or thrombopoietin
• Diabetes mellitus
• Respiratory diseases
• Sepsis
• Hyperthyroidism
• Pre-eclampsia (toxemia of pregnancy) and HELLP syndrome
• Heart disease or artificial heart valves

Platelet count and volume can be affected by factors such as altitude, hormones, and health risk factors:

• People who live at low altitudes (below sea level) may have higher than average platelet counts, while those who live at high altitudes may have a high MPV, which has been considered a possible risk factor for heart disease.
• Smoking, high blood pressure, and high glucose levels (without a diagnosis of diabetes) have all been associated with a high MPV in men, while menstruation and oral contraceptives are associated with high MPV in women.
• Strenuous exercise has also been associated with an increase in platelet count if it is severe enough to cause tissue damage.

It is important to keep these factors in mind, knowing that your platelet count and MPV may undergo some variation.

A low MPV generally suggests that most of your platelets are older and that your bone marrow has slowed down production of platelets. Here too, your total platelet count can help provide insight about the cause.

A low MPV with the following platelet counts can suggest associated conditions:

• A low platelet count along with low MPV points toward bone marrow disorders that slow down or decrease the production of platelets, such as aplastic anemia.
• A high platelet count along with low MPV often signifies an infection, inflammation, or cancer.
• A normal platelet count along with low MPV is common with chronic kidney failure.

Conditions that may be associated with a low MPV and variable platelet counts include:

• Bone marrow failure
• Lupus
• Splenomegaly (an enlargement of the spleen), which often causes platelets to be trapped in the spleen
• Medications that suppress platelet formation, such as chemotherapy
• Hypothyroidism
• Iron deficiency anemia
• HIV/AIDS

While MPV is a helpful test, it is not diagnostic. And some conditions, such as cancer, can be associated with a low or a high MPV. Your MPV results are considered along with your other symptoms. For example, you may need a thyroid test if you have symptoms of hyperthyroidism or hypothyroidism.

Similarly, if you have unexplained weight loss or bruising with an elevated or low MPV, you may need further testing with a bone marrow biopsy, which can identify certain types of cancer and may determine whether your bone marrow is not functioning as it should.

Some studies suggest that MPV may be associated with predicting conditions such as heart attacks and strokes. Similarly, there may be an association between MPV and some nutritional deficiencies such as vitamin D and vitamin B12. Overall, while it is certainly a helpful value to consider, MPV should be considered along with your overall health status and your other lab results.