Plateletcrit (PCT, plateletcrit) is the fraction of blood volume occupied by platelets. It is the platelet analogue of the hematocrit: the value reflects their total "mass" in the blood.
Plateletcrit is calculated from the platelet count and their mean volume (MPV) and complements PDW in the complete blood count.
Reference ranges
Plateletcrit is expressed as a percentage; approximate values for adults:
| Plateletcrit (PCT) | ≈ 0.17 – 0.35% |
| Formula | PCT = platelets × MPV / 10,000 |
| Assessed with | platelet count and MPV |
What an elevated level means
A high plateletcrit means an increased total platelet mass — usually with thrombocytosis. Causes: reactive thrombocytosis in inflammation, infection, iron deficiency, and myeloproliferative disorders. A high plateletcrit may be accompanied by an increased risk of thrombosis.
What a low level means
A low plateletcrit reflects thrombocytopenia — platelets are few or small. This occurs with bone-marrow suppression, increased platelet destruction, and diseases of the liver and spleen. A marked reduction raises the risk of bleeding.
How the test is done
Plateletcrit is calculated automatically in a routine complete blood count — no special preparation is needed. As a calculated value, it depends entirely on the accuracy of the platelet count, so it is assessed together with the platelet number, MPV and inflammatory markers.
What affects the value
- Clots in the sample lower the platelet count and plateletcrit.
- Pseudothrombocytopenia due to EDTA (platelet clumping) distorts the result.
- Different analyzers count plateletcrit differently.
Frequently asked questions
How does plateletcrit differ from the platelet count?
The platelet count is their number, while plateletcrit is the fraction of blood volume they occupy, taking size (MPV) into account. Sometimes, with a normal count but large platelets, the plateletcrit is higher, so it complements rather than replaces the ordinary count.
Is a plateletcrit above normal dangerous?
A high plateletcrit most often reflects reactive thrombocytosis (inflammation, infection, iron deficiency) and resolves along with its cause. Persistently high values call for ruling out bone-marrow disease and having a doctor assess the risk of thrombosis.