What are Platelet indices (PI)?

Platelet parameters, which include the Plateletcrit (PCT), platelet distribution width (PDW) and Mean Platelet Volume (MPV), have been available in the laboratory routine using blood cell counters for several years.

These 3 platelet indices are a group of derived platelet parameters that are obtained as part of the automatic analysis of the complete blood count (CBC). Those platelet indices may have diagnostic and prognostic value in certain diseases. Platelets are dynamic blood particles whose primary function, along with the coagulation factors, haemostasis, or the prevention of bleeding. In addition to their important role in haemostasis and thrombosis, accumulating evidence demonstrates that platelets contribute to the inflammatory process, microbial host defense, wound healing, angiogenesis, and remodeling.

MPV (more info here):

When platelet production is decreased, young platelets become bigger and more active, and MPV levels increase. Increased MPV indicates increased platelet diameter, which can be used as a marker of production rate and platelet activation. During activation, platelets’ shapes change from biconcave discs to spherical, and a pronounced pseudopod formation occurs that leads to MPV increase during platelet activation.

PDW:

PDW directly measures variability in platelet size, changes with platelet activation, and reflects the heterogeneity in platelet morphology. Under physiological conditions, there is a direct relationship between MPV and PDW; both usually change in the same direction. Meanwhile, there are conflicting reports in the literature about the relationship between platelet volume and numbers, which suggests that they are affected by different mechanisms.

PCT:

PCT (Plateletcrit) is the volume occupied by platelets in the blood as a percentage and calculated according to the formula PCT = platelet count × MPV / 10,000 (25-27). Under physiological conditions, the amount of platelets in the blood is maintained in an equilibrium state by regeneration and elimination. The normal range for PCT is 0.22–0.24%. In healthy subjects, platelet mass is closely regulated to keep it constant, while MPV is inversely related to platelet counts. Genetic and acquired factors, such as race, age, smoking status, alcohol consumption, and physical activity, modify blood platelet count and MPV.

Simultaneous measurement of all of the platelet indices will provide a valid instrument for measuring disease severity and an insight into the potential etiology that resulted in platelets’ indices changes.

Platelets play an important role in inflammation, and recently, several additional functions for platelets in the process of inflammation were defined. A substantial number of studies have demonstrated crucial roles for platelets in the pathogenesis of various inflammatory clinical conditions where inflammation is important. Numerous research groups have found a relationship between the changes in platelet indices and the activation of the coagulation system, severe infection, trauma, systemic inflammatory reaction syndrome, and thrombotic diseases. Platelet indices have been shown to have diagnostic value in certain inflammatory diseases, such as inflammatory bowel diseases, rheumatoid arthritis, ankylosing spondylitis, ulcerative colitis, and atherosclerosis.

MPV acts as a negative or positive acute phase reactant in different inflammatory conditions. High MPV levels are associated with high-grade inflammation owing to the presence of the large platelets in circulation. MPV might decrease in high-grade inflammation due to the consumption and sequestration of these large platelets in the vascular segments of the inflammatory region. Low MPV is associated with low-grade inflammation, like rheumatoid arthritis and attacks of familial Mediterranean fever. MPV decreases and increases in acute and chronic disorders, respectively.

MPV shows the activity of disease in systemic inflammation, acute pancreatitis, unstable angina, and myocardial infarction. MPV can be a modifiable marker in identifying patients with active ankylosing spondylitis and rheumatoid arthritis, which is thought to be due to increased consumption of platelets in the inflammation area and MPV increases with therapy in these patients.

Platelet indices especially MPV, may be a simple way to provide valuable information during routine blood counts without increasing the cost of diagnosis.

Source: “The use of platelet indices, plateletcrit, mean platelet volume and platelet distribution width in emergency non-traumatic abdominal surgery: a systematic review.”

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4910273/

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