Identification and validation of a factor of commutability between platelet counts performed on EDTA and citrate

The anticoagulant mostly employed for platelet count is EDTA. The Francophone Group of Cellular Hematology recommends checking of blood smear stained with May-Grnwald Giemsa any thrombocytopenia less than 100 G/L without medical history or whether an alarm is generated by the cell counter. The pseudo-thrombocytopenia (PTP) with EDTA is the best known artifact in platelet count. A sample of blood on citrated tube is necessary to get rid of the interference. The objective of this study was to compare the platelet counts obtained on EDTA (numEDTA) and citrate (numCTAD) tubes and to define, then validate a factor of conversion between both methods. The prevalence of PTPEDTAis 0.26%. The PTP was transient in 80% of the patients. The numEDTA and numCTAD+10% (numCTAD increased by 10% to take dilution into account) are correlated but are not equivalent. The num CTAD+10% underestimate numEDTA significantly. The systematic bias is removed if we increase by 17% numCTAD. The factor of correction is stable over a period of 3 hours.