Pseudothrombocytopenia in cats: platelet clumping
7-year-old cat at a senior health check, with no bleeding or petechiae. Sampling was slow and the cat struggled. The impedance analyser reports:
| Parameter | Result | Reference |
|---|---|---|
| Platelets | 48,000/µL | 300,000–800,000 |
| Haematocrit | 36% | 30–45 |
| White blood cells | 9,800/µL | 5,500–19,500 |
What is the most appropriate next step?
chevron_right Show answer and explanation
A. Start prednisolone for suspected immune-mediated thrombocytopenia
Primary immune-mediated thrombocytopenia is rare in cats and this cat is not bleeding. Treating without confirming the count is a common mistake.
B. Transfuse platelet-rich plasma before any procedure
There is no bleeding and the count is unconfirmed. Platelet transfusions are reserved for severe bleeding with true thrombocytopenia.
C. Bone marrow aspirate to assess megakaryocytes
It is an invasive test indicated only for true, persistent thrombocytopenia without a peripheral cause. The count must be confirmed first.
D. Review the smear (especially the feathered edge) for clumps and estimate the count
Correct. Feline platelets clump easily and are large, so analysers undercount them or count them as red cells. Each platelet per oil-immersion field equals about 15,000–20,000/µL; if there are clumps, repeat with a clean venepuncture.
lightbulb Key takeaway
In cats, thrombocytopenia without bleeding is pseudothrombocytopenia until the smear proves otherwise. To reduce clumping: quick, clean sampling, correct tube filling and prompt analysis; a citrate tube may help.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.