Interference of blast cell fragments with automated platelet counting

Introduction: Automated haematology analysers may inaccurately determine platelet counts in several circumstances. Spuriously elevated automated platelet counts have been reported in some acute leukaemia (AL) cases because of fragmentation of circulating blast cells (pseudoplatelets). Haemorrhagic diathesis is a common manifestation of AL, which is often caused by severe thrombocytopenia. Therefore, overestimation of the actual platelet count in patients with AL can affect its clinical management. We aimed to detect the frequency of pseudoplatelets in patients with AL. Methods: Complete blood cell counts were performed on 86 AL patients with three automated analysers (ADVIA 2120, Coulter LH 750 and Sysmex XE-2100D). Platelet counts were also performed by quantitative flow cytometry (QFC). The platelet counts of the automatic analysers were compared to the platelet counts by QFC. Blood smears were checked for the presence of pseudoplatelets. Results: The automated analysers overestimated the platelet count due to the presence of pseudoplatelets in patients with AL. Pseudoplatelets were observed in the blood smears of 11 patients (13%). Three of these patients were near the prophylactic platelet transfusion threshold. Conclusion: Spurious increases in automated platelet counts by blast cell fragments are little known but frequent artefacts that should be ruled out by careful examination of peripheral blood smears.