Platelet Quality

Platelet concentrates are primarily comprised of plasma (the medium), platelets, and microparticles (small pieces of platelets that have fractured from the cells over time). Historically, platelet concentrates have been considered “good” if the platelet count was high enough, or in other words, that there were enough platelets in a given volume. Samples would be taken from the platelet concentrate and analysed using automated cell counters to determine the platelet count. However, the platelet count method does not take into account the functionality of the platelets; therefore it is a poor predictor of platelet quality.
There are two additional indicators of platelet quality that are important to consider: the temperature response of the platelets, and the presence of microparticles.

Platelets respond to temperature variation, and when cooled they “activate” to form pseudopods: radial tentacles emanating from the normally smooth, discoid cell. Viable platelets will activate readily when heated or cooled, whereas non-viable platelets will not respond to temperature stress.

The presence of microparticles is also an indicator of platelet quality. Over time, small pieces of the platelet pseudopods fracture from the cells to cause “microparticles”. Higher quality platelet concentrates have fewer microparticles, indicating that the platelets are intact and have not broken down.

The overall quality of the platelet concentrate can therefore be determined by considering the platelet count, the temperature response of the platelets, and the ratio of microparticles to platelets.