Objectives: There are conflicting reports on the reliable measurement of platelet count and mean platelet volume (MPV) using EDTA or citrate. The anticoagulant properties of magnesium sulfate (MgSO4) are known from the literature. The aim of this study was to evaluate MgSO4 as an in vitro anticoagulant for platelet count, MPV, platelet distribution width, and platelet activation.
Methods: Whole blood from volunteers was anticoagulated by EDTA, citrate, or MgSO4. Platelets were counted by the XE 5000 (Sysmex, Norderstedt, Germany) impedance and fluorescence optical technique.
Results: The mean impedance platelet counts were 227.7, 197.0, and 201.1 × 109/L in EDTA-, citrate-, or MgSO4-anticoagulated blood, respectively. The counts were 4.7% higher (EDTA) after 3 hours of storage but 4% lower in citrate-anticoagulated blood. The counts in magnesium samples remained stable. The MPV was 10.4 fL (EDTA), 9.5 fL (citrate), and 9.3 fL (MgSO4). EDTA samples showed cell swelling within the first 3 hours. This was lower in citrate and only marginal in magnesium samples. High activation of platelets was observed only in EDTA samples.
Conclusions: Magnesium anticoagulation might be advantageous for more reliable MPV measurements. Although platelet count is underestimated when the impedance method is used, the platelet count reveals similar results when measured by the fluorescent optical method.