Objectives: Magnesium sulfate (MgSO4) was recently reported as an alternative in vitro anticoagulant in pseudo-thrombocytopenia. Its suitability as an anticoagulant for the determination of reliable platelet parameters is the subject of this study.
Methods: Platelet count and mean platelet volume were measured in blood samples anticoagulated with EDTA and MgSO4 and compared. The platelet parameters were determined by impedance (XE 5000 [Sysmex, Norderstedt, Germany]; DxH 800 [Beckman-Coulter, Krefeld, Germany]) and laser light-scatter technology (Advia 120 [Siemens Healthcare Diagnostics, Eschborn, Germany]).
Results: MgSO4 anticoagulation underestimated platelet counts compared with EDTA. Mean platelet volume (MPV) in magnesium-anticoagulated blood was lower when measured by impedance but higher when light-scatter technology was used. Storage of the differently anticoagulated blood led to differently lower platelet counts after 24 hours, independent of the anticoagulant. In EDTA blood, the mean platelet volume increased moderately when measured by impedance but markedly when measured by laser light scatter. In MgSO4-anticoagulated blood, the MPV increase was negligible.
Conclusions: Impedance technology and magnesium anticoagulation might be advantageous for standardizing MPV measurements, although the mean platelet count is slightly underestimated by both technologies.