Plateletcrit
What it measures, and what changes the number.
Plateletcrit is the share of a blood sample's volume taken up by platelets, the small cell fragments that help blood clot. It is not measured directly but calculated by the automated blood counter from the platelet count and the average platelet size, much as hematocrit is for red cells.
It appears on the full blood count next to the platelet count, mean platelet volume and platelet distribution width. Together these describe both how many platelets there are and how large they are.
The sample is drawn into an anticoagulant tube. Platelets can swell the longer the tube sits before analysis, and they sometimes clump in the tube, which shifts the calculated figure. Analyzer brands use different methods, and not every lab reports this value. It may be listed as Plaquetòcrit or PCT.