Platelet Clumping

Thrombocytopenia (low platelet count) is a common indication for a blood film both from automated flags and at clinician request. One of the important findings in the peripheral film is to identify where the platelets may not be correclty identified by the analyser. Platelets can be undercounted if they are large, clumped or stuck to other cells such as neutrophils. Platelet numbers can be overestimated where there are red cell fragments as the analyser identifies a platelet only by it's apparent size.

This film shows large platelet clumps and platelet satellistism around the neutrophils.

When looking over the film you should be reviewing the trails and edges which is where clumps often appear more frequently. The presence of even small clumps can be relevant as these will not be accurately counted by the analyzer. Vigorous clumping, such as that seen in this film, is not common but when it occurs the reported platelet count may be extremely low but in reality is most likely normal.

Platelet clumping occurs in a small number (1-3%) of the normal population and is a platelet response to the EDTA anticoagulant used in the FBC tubes. This is not an illness and does not require any specific treatment. The recommendation from the film should be that the clinical team check a citrated platelet count (a platelet count checked on a blue top/citrate sample) which is less likely to clump.

If the clinical history indicates pregnancy or imminent surgery then it may be useful to flag these films to the haematology clinician as they may get a call about the patient, but otherwise the finding can be recorded and does not require any specific intervention.