Platelets – Part 3 – Platelet Indices

Platelet Indices

This is the automated calculation of the platelets indices which consists of:

1. Mean platelet volume (MPV).
2. Plateletcrit (Pct).
3. Platelet distribution width (PDW).

Indications

1. Platelet indices are potentially useful markers for the early diagnosis of thromboembolic diseases.
2. MPV and PDW help in discriminating causes of thrombocytopenia as hypoproductive or hyper-destructive like immune thrombocytopenic purpura.
3. An increase in both mean platelet volume (MPV) and platelet distribution width (PDW) due to platelet activation, was suggested due to :
   1. Platelet swelling.
   2. Pseudopodia formation.
   3. MPV and PDW are simple platelet indices, which increase during platelet activation.

Mean Platelet Volume (MPV)

• Definition: MPV is a machine-calculated measurement of the average size of platelets found in blood and is typically included in blood tests as part of the CBC.
  1. Primarily with thrombocytopenia when it is due to:
     1. Impaired production as in aplastic anemia.
  1. MPV is higher when there is the destruction of platelets.
     1. This may be seen as inflammatory bowel disease.
     2. In immune thrombocytopenic purpura (ITP).
     3. In myeloproliferative diseases and Bernard-Soulier syndrome.
     4. It may also be related to preeclampsia and recovery from transient hypoplasia.
  2. Low MPV values will be associated with bleeding.
  3. In the case of the release of immature platelets to the circulation, which is larger in size leads to raised MPV.
  4. In the case of ineffective platelet formation in the bone marrow, as their size is smaller then there is low MPV.
     1. MPV is very useful in the case of thrombocytopenia.

Plateletcrit (Pct)

1. Plateletcrit is an effective screening tool for detecting platelet quantitative abnormalities.
2. Normal platelet count has a Plateletcrit within the range of 0.20 to 0.36%.
3. Normal Values
   1. The average of Mean platelet volume was 9.13 fl.
   2. Plateletcrit- 0.23%.
   3. Platelet distribution width – 56.6% of normal platelet counts.
4. Sensitivity and specificity for detection of :
   1. Thrombocytopenia at the Plateletcrit cutoff range of 0.20 – 0.36% is 97 and 80%.
   2. Thrombocytosis is 94 and 98%.

Platelet distribution width (PDW)

1. PDW is a simple, practical, and specific marker of activation of coagulation.
2. PDW is a more specific marker of platelet activation since it does not increase during simple platelet swelling.
3. PDW has been receiving attention due to its usefulness for distinguishing between reactive thrombocytosis and thrombocytosis associated with the myeloproliferative disorder.
4. The determination of the PDW reference range is fundamental.
5. Mean platelet volume (MPV) and platelet distribution width (PDW) are useful in the differential diagnosis of aplastic anemia and idiopathic thrombocytopenic purpura.
6. An increased PDW is an indication of the anisocytosis of platelets.
7. Standard PDW ranges from 9 to 14 fL.