title: EDTA-dependent pseudothrombocytopenia: further insights and recommendations for prevention of a clinically threatening artifact.
abstract: Ethylenediaminetetra-acetic acid (EDTA) is widely used as anticoagulant in laboratory medicine. EDTA-dependent pseudothrombocytopenia is a rare phenomenon (i.e., around 0.1% in the general population), which is mostly due to the presence of EDTA-dependent antiplatelet antibodies that react optimally between 0°C and 4°C, recognize the cytoadhesive receptors gpIIb-IIIa, stimulate the expression of activation antigens, trigger activation of tyrosine kinase, platelet agglutination and clumping in vitro, which finally lead to a spuriously decreased platelet count. The reliable and timely identification of this artifact is essential, since there a high chance that it may be confused with other life-threatening platelet disorders, or otherwise lead to inappropriate clinical and therapeutic decision-making. Five basic criteria should be fulfilled to raise the clinical suspicion of EDTA-dependent pseudothrombocytopenia, i.e., (i) abnormal platelet count, typically <100×10(9)/L; (ii) occurrence of thrombocytopenia in EDTA-anticoagulated samples at room temperature, but to a much lesser extent in samples collected with other anticoagulants and/or kept warmed at ~37°C; (iii) time-dependent fall of platelet count in the EDTA specimen; (iv) evidence of platelet aggregates and clumps in EDTA-anticoagulated samples with either automated cell counting or microscopic analysis; (v) lack of signs or symptoms of platelet disorders. Several remedies have been proposed, such as warming the sample to 37°C or using additives or specific formulations of anticoagulants including buffered sodium citrate, heparin, ammonium oxalate, β-hydroxyethyltheophylline, sodium fluoride, CPT (trisodium citrate, pyridoxal 5'-phosphate and Tris), antiplatelet agents, potassium azide, amikacin, kanamycin or other aminoglycosides, and calcium replacement with the simultaneous addition of calcium chloride/heparin. According to available evidences, the most suitable and practical approach so far for most clinical laboratories seems, however, the recollection of blood samples using sodium citrate, CPT or calcium chloride/heparin as additives, maintaining the specimen at 37°C until the platelet count has been completed.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Lippi
authors.forename: Mario
authors.initials: M
authors.lastname: Plebani
mesh_terms: D000925:Anticoagulants / Q000009:adverse effects* / Q000494:pharmacology; D004492:Edetic Acid / Q000009:adverse effects* / Q000494:pharmacology; D006801:Humans; D013921:Thrombocytopenia / Q000097:blood / Q000473:pathology / Q000517:prevention & control*
chemical_list: D000925:Anticoagulants; D004492:Edetic Acid