Pseudothrombocytopenia consists in a false reduced number of platelets count in blood samples collected into EDTA-containing vials. This reduction may be due either to platelets agglutination or, seldom, to platelets rosettes formation around neutrophils, a phenomenon known as platelet sathelitism. The physiopathological nature of the EDTA-induced pseudothrombolytopenia is still uncertain. However, it has been proposed that plasma autoantibodies may recognise and bind to the glycoprotein IIb (GPIIb) epytope, which is part of the GPIIb/IIIa complex on the platelet surface, promoting platelet agglutination. It is quite important to know the clinical data from patient in order to prevent spurious results. As pseudothrombocytopenia is suspected, diagnosis can be confirmed by counting platelets immediately following EDTA blood sampling and after 1 or 4 hours, as it is verified a gradual reduction of the previous results. The correct platelet number can be determined by blood collection in 3,8% sodium citrate and performing platelet count immediately. A minucious observation of the blood smear is indispensable for pseudothrombocytopenia characterization. It will be evident platelet clumps, which are more frequent on the smear tail. Also, it may be observed in blood smears the presence of plateled sathelitism, both resulting in a false reduced platelet count. A minucious and careful hystogram observation may also suggest pseudothrombocytopenia, as a cellular debris increase is present.
Pseudothrombocytopenia; Sathelitism; EDTA; GPIIb/IIIa
