Spurious platelet counts in acute leukaemia with DIC due to cell fragmentation.

Automated platelet counts in a patient with newly diagnosed AML M5 with extreme leukocytosis were reported as 129, 166 and 121 x 10(9)/1. Routine blood films showed a corresponding number of platelet-sized particles, judged to be platelets. The patient was treated for DIC with low-dose heparin infusion. Platelet transfusions were not given initially. The patient died 14 h after admission from intracerebral haematoma. The origin of the platelet-sized particles seen in routine stained blood films was examined by cytochemical and immunological staining for peroxidase, non-specific esterase, CD 13 and CD 33. About 1/3 of the fragments had the same staining characteristics as the leukaemia cells, indicating leukaemia cell origin. Staining for platelet-specific antigen GpIIIa was positive only in 4% of the platelet-sized fragments, with a calculated true platelet count of 4 x 10(9)/1. The presence of cell fragments masquerading as platelets should be suspected in leukaemia patients with bleeding symptoms and normal or near normal platelet counts.