Thrombocytes indices are values obtained by calculation. They can help to evaluate the characteristics of thrombocytes.
Electronic counters can calculate 2 numeric indices of thrombocytes on the basis of their absolute number and histogram:
- PDW (platelet distribution width), and
- MPV (mean platelet volume).
By determining MPV and PDW, it is possible to differ hyperdestructive from hypoproliferative thrombocytopenia.
Reference values:
PDW = 9.4 – 10.6
PDW values can indicate:
- if there are great and small thrombocytes in the blood sample;
- if thrombocytes are normally distributed;
- if there is a technical error; and
- if the measured cells are the thrombocytes.
MPV (mean platelet volume)
MPV normally has an inverse relationship to the platelet count. Platelets swell 15-25% during the first 2 hours in the blood anticoagulated with EDTA, and the interpretation of the MPV is therefore difficult. However, MPV may be useful in certain cases where it typically increases, such as hyperthyroidism, myeloproliferative disease, and during neonatal coagulase-negative staphylococcal sepsis, provided that the conditions are carefully controlled.
MPV is calculated as follows:
Thrombocytocrit (Tct)
Thrombocytocrit (Tct) = PDW x thrombocyte count
Thrombocytocrit (Tct) = volume % of thrombocytes
This formula is valid for erythrocytes and thrombocytes on the part of the blood smear where they are distributed according to the Gaussian curve.
Reference values:
MPV = 6.8 - 10.4 fl
Tct = 0.15 - 0.32 % |
