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Platelet Clumps on Blood Film

Susan Lemire asks, “Hi, what are most people doing when platelet clumps are found on the blood smear, but the platelet count is within normal range?”

Hi, Susan, my hunch is that since we don’t review blood films when the CBC is within acceptable parameters, we probably miss some platelet clumping. CBC profiling instruments do flash an indication if the clumps cause an elevated MPV, however. Platelet clumping often signals platelet activation and possible early clot formation in a poorly mixed or vigorously shaken EDTA specimen (or slowly collecting a capillary specimen), though it could also be seen in platelet satellitosis. In satellitosis, the platelet count usually drops to below the lower limit of the reference interval and would be flagged by the instrument. In some labs we gently vortex the specimen and repeat the CBC with blood film exam, however the recommended approach is to collect a fresh specimen, observing the mixing protocol. In the case of satellitosis, collect the platelet count specimen in a sodium citrate tube. Thank you for your question, and as always, I invite comments from our participants.

Comments (1)
Platelet Function Testing
Aug 31, 2016 12:13pm

I concur. This is likely due
I concur. This is likely due to not mixing the sample immediately upon collection, or mixing it too vigorously. Capillary EDTA tubes are especially susceptible to platelet clumping during collection if the site wasn’t prewarmed and the tube fills slowly.

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