Impact of Shaking EDTA, Citrate, or MgSO₄ Tubes on Platelet Count Results

Background: In EDTA-induced pseudothrombopenia, citrate or MgSO₄ are recommended for platelet counting. Pre-analytical conditions are poorly defined for tubes containing MgSO₄ or citrate. In this study, we analyzed the impact of agitation of these tubes on platelet counts. Methods: K2EDTA, citrate, and MgSO₄ tubes from 70 patients were gently agitated on a wheel rotating at 20 rpm. Platelets were analyzed on the Sysmex XN analyzer at different times, and the percentage of platelet deviation from T0 was assessed and compared with the desirable bias of the EFLM. Results: at 180 min in fluorescence, the relative variation of platelets after shaking is 1.17% for K2EDTA, -29.76% for citrate, and -33.18% for MgSO₄, while for unshaken MgSO₄ platelets the variation is -1.3%. The reduction in platelet numbers when citrate or MgSO₄ tubes are shaken is linked to the appearance of platelet clusters. Conclusions: agitation of MgSO₄ and especially citrate tubes led to a decrease in platelet counts due to the formation of platelet aggregates; on the other hand, platelet counts on EDTA are virtually stable. During transport, we recommend putting sodium citrate and MgSO₄ tubes in an upright position and avoiding shaking them to avoid giving an erroneous platelet result.