Wright's stain, 400x

Clumps of aggregated platelets are often found on the feathered edge of blood smears and may be readily observed (if large enough platelet clumping occurs) at low magnification (100x). Note the clumped as well as individual platelets on the periphery of the clump (arrow). Platelet aggregation is common in animals and generally occurs while collecting the sample. Horses and cats are more prone to platelet clumping than other species. It is important to check for platelet clumps on the blood smear when the automated platelet count (by a particle counter) is low, as it may be an artefactually low count. See : thrombocytopenia