Plateletcrit (PCT) in cats and dogs
Plateletcrit (PCT) is the share of blood volume taken up by platelets, in percent — the platelet counterpart of the hematocrit. Most analyzers calculate it from the platelet count and the mean platelet volume, so it reflects the total platelet mass rather than the number of cells. It is most useful when the count is low but the platelets are large.
What it shows
Platelets are small cell fragments that start blood clotting. The platelet count tells how many there are; the plateletcrit tells how much room they take up together. eClinPath describes it as analogous to the hematocrit: it reflects the mass of platelets.
There are two ways to get it. Laser-based analyzers calculate it by multiplying the platelet count by the MPV (the average platelet volume) and expressing the result as a percentage of blood volume. Buffy-coat analyzers measure it directly from the layer of cells in a spun tube. The laser method tends to give lower values than the buffy-coat method, and it is not yet clear which is better — one more reason to compare results from the same analyzer.
Why it matters: the same number of platelets can carry a different total mass. If platelets are fewer but larger, the plateletcrit can stay normal, and the animal’s ability to form a clot may be better than the count alone suggests.
Higher than reference — what it may be a sign of
- More platelets: since the plateletcrit is built from the count, anything that raises the count raises it too. The meaning is the same as for a high platelet count.
- Larger platelets: a higher MPV with the same count raises the plateletcrit.
- An old sample: platelets swell while the blood waits in the tube; eClinPath notes that storage is likely to raise the plateletcrit falsely.
Lower than reference
A low plateletcrit means a low total platelet mass — usually because the count is low. Then the question is the same as for a low platelet count: whether platelets are truly lacking or only appear to be.
- Platelet clumps: clumps are not counted as individual platelets, so the calculated value can drop. Clumping is especially frequent in cats, and a vet checks the smear.
- Breed: eClinPath notes that greyhounds can have lower platelet counts and lower plateletcrits than other dogs.
- True loss of platelets: increased use, destruction or reduced production; the vet sorts this out with the full blood count and other tests.
eClinPath suggests that plateletcrit may help tell a true low count from an artefactual one, but notes that this has not yet been tested.
Look at together with
- Platelet count — the main number; the plateletcrit adds whether the platelet mass is preserved.
- MPV — the second half of the formula: a normal plateletcrit with a low count usually means large platelets.
- Blood smear review — rules out clumps before conclusions are drawn.
Units and conversion
Plateletcrit is reported in percent (%): the share of blood volume taken up by platelets. Values are small, around tenths of a percent, so the decimal point matters when the result is copied. There is only one unit, and no conversion is needed. Because the calculated and directly measured plateletcrit differ, it is best to follow the trend on one analyzer.
Reference range
The reference range is on your lab’s form. It depends on the analyzer and the method: calculated and measured plateletcrit give different numbers, and storage of the sample shifts the result. The plateletcrit is read only together with the platelet count, the MPV and the smear; on its own it does not make a diagnosis.
Cats and dogs
In cats platelets clump easily, and clumps lower the calculated platelet count and, with it, the plateletcrit. A low value in a cat without bleeding signs is first checked against the smear. There are no separate plateletcrit data for cats in the sources used here.
In dogs the plateletcrit is most useful in Cavalier King Charles spaniels with inherited macrothrombocytopenia. Their platelets are uniformly large, so a mild to moderate drop in count goes with a normal plateletcrit — in an eClinPath case, a count of 71 thousand/µL with a plateletcrit of 0.16% and no bleeding. Greyhounds can have lower plateletcrits than other breeds.
Add a lab form — Pet Tracker Space recognises the lines, keeps the form’s units and draws each indicator over time with your lab’s reference band.
Sources
This page explains what a lab value means. It is not a diagnosis and not a substitute for your veterinarian — only they can interpret results for your pet.