The response to infusion of random donor platelets can be evaluated by calculating the corrected count increment (P):
p = C × S/U (platelets/L)
Where C = measured platelet increase (platelets/L)
S = body surface area in square meters
U = number of units of platelet given
Average corrected count increment is 10 × 109/L.
In a single-donor plateletpheresis product, there are about the same number of platelets as in five random-donor units.
The 20-hour increment is two-thirds of the 1-hour increment under normal conditions (absence of alloimmunization, ongoing hyperconsumption of disseminated intravascular coagulation or bleeding, or pooling in an enlarged spleen).
Additional factors that lower the corrected count increment are loss of platelet viability in storage, stem cell transplantation, or drug therapies (eg, amphotericin).