MPV: high or low, mean platelet volume analysis

The MPV, mean platelet volume, is a platelet size index, which constitute the smallest components of the blood and are moreover extremely reactive elements. Platelets are also called thrombocytes.

• Platelets are useful for blood clotting. They participate in stopping bleeding during an alteration of the wall of blood vessels (arteries or veins). They are activated in the event of internal bleeding as in the event of external bleeding;
• Platelets are produced in the bone marrow, within which a huge cell (called a megakaryocyte) bursts into thousands of small fragments. These fragments, called platelets, become active once they enter the bloodstream;
• It is possible to count platelets, but also to measure their volume by means of an analyzer using a light beam.

Large platelets are usually younger, and have been released earlier than usual from the bone marrow. Conversely, smaller-than-average platelets are generally older.

Normally there is an inverse relationship between the mean platelet volume (MPV) and the number of platelets. There is, thus, a natural regulation of the total platelet mass (combination of the number and the size of the platelets). This implies that a decrease in the number of platelets causes stimulation of megakaryocytes by thrombopoietin, resulting in the production of larger platelets.

• The normal level of platelets in the blood (their quantity) is generally between 150 and 000 platelets per cubic millimeter;
• The MPV, which measures their size, and therefore their volume, is measured in femtoliters (a metric unit of volume equal to 10^-15% liters). A normal MPV is between 6 and 10 femtoliters.

You should know that platelets with a higher volume are more active. Finally, in the absence of pathology, the total mass of platelets is controlled, and the mean platelet volume (MPV) therefore tends to rise as soon as the number of platelets is lowered.

The average platelet volume can be affected in connection with certain platelet pathologies. And it is, in particular, the quality of the platelets that can be modified in the event of abnormal MPV.

During thrombocytopenia, and therefore an abnormal decrease in the number of platelets, it may be useful to monitor the MPV, as well as in the event of thrombocytosis (increased platelet count) or other thrombopathies (diseases for which the number of platelets is normal but the functioning of which is faulty). 

The MPV also seems to be associated more particularly with the cardiac risk, for which it remains little used in practice, because there are technical difficulties interfering with the measurements. In fact, when there is a cardiovascular risk or a risk of thrombosis, such as phlebitis, this can be correlated with a high MPV.

In this sense, several research works carried out during the last twenty years stipulate that the MPV would be interesting to provide important information in the development and the prognosis related to various inflammatory conditions. 

Thus, this research reveals that a high MPV has been observed in association with many pathologies:

• Cardiovascular diseases;
• Strokes;
• Respiratory diseases;
• Chronic renal failure;
• Intestinal diseases;
• Rheumatoid diseases;
• Diabetes;
• Various cancers.

Conversely, a MPV decreased can be observed in the following cases:

• Tuberculosis, during the exacerbation phases of the disease;
• Ulcerative colitis;
• Systemic lupus erythematosus in adults;
• Different neoplastic diseases (abnormal development and proliferation of cells).

This is why, from a clinical point of view, it would be interesting to establish threshold values ​​of MPV capable of indicating, among other things, the intensity of an inflammatory process, the presence of a disease, the increased risk of developing disease, the increased risk of thrombotic complications, the increased risk of death and, finally, the patient’s response to the treatments applied. However, in clinical practice, these uses of MPV are still limited and require further research.

A simple blood test is necessary for the analysis of the mean platelet volume. Thus, the MPV is generally measured during a relatively frequent examination: the blood count (or CBC), a complete examination of the blood which makes it possible in particular to count all its elements (red blood cells, white blood cells and platelets). In practice, it is advisable to take the blood sample on an empty stomach.

The MPV analysis, carried out on the tubes taken during the blood test, is carried out by means of an automated method, which has been used since the 1970s, and called in English “light scattering”:

• The principle of this examination is to illuminate the cells with a laser or tungsten light;
• The light disseminated by each cell is captured by a photodetector, then converted into electrical impulse;
• Thus, the analyzer will be able to calculate the average volume of thousands of platelets which circulate by passing them through a beam;
• The calculation of the mean platelet volume, MPV, is finally performed by means of a logarithmic transformation of the platelet volume distribution curve.

To interpret the mean platelet volume results, you should always have first first checked the platelet count associated with MPV. This number of platelets may be reduced in the event of thrombocytopenia, or on the contrary increased in the event of thrombocytosis.

• Un high MPV means that a large number of large platelets are circulating in the blood;
• Un MPV base conversely, means that the person has a large number of small platelets.

The results should always be analyzed in correlation with the data of the clinic, but also with the other results of the blood count. Often, abnormal results will require additional testing.

In addition, under certain conditions, the platelets can group together. They then seem to be present in small quantities and or appear to be increased in size: a sample must be taken in order to examine the platelets directly under a microscope.

Ultimately:

• Although a bone marrow dysfunction cannot be ruled out in the event of abnormal MPV, causes which do not involve the bone marrow are also common: inflammatory diseases ou maladies autoimmune destroying platelets;
• A low thrombocytopenia (lower than normal number of platelets) associated with a low MPV is rather related to a suppression of the production of cells by the marrow: it can be a question ofanemia. A low MPV may also be associated with sequestration splenic (in the spleen) especially since it is then the largest platelets which are sequestered;
• In a person with no previous history of bleeding, and with a normal number of platelets, an abnormal MPV is of less clinical utility. So the MPV can simply vary from physiological way, and without there being any link with any pathology.