Platelet clumping

If patients have repeated full blood counts which describe platelet clumping, ‘no platelet count’ will be reported. Platelet clumping can lead to falsely low automated platelet counts.

Platelet clumping can occur due to platelet activation while samples are being taken (difficult venepuncture), or, in some patients, due to antibodies which react with the EDTA within the FBC tubes causing platelet aggregation.   

Please initially repeat sample in the normal way, but if there is ongoing clumping:

Send a FBC sample (EDTA) and a citrate tube marking the sample indication as “previous platelet clumping”

If thrombocytopenia persists when no clumping is reported, please refer to the RefHelp thrombocytopenia guidance.