EDTA‐dependent pseudothrombocytopenia: A clinical and epidemiological study of 112 cases, with 10‐year follow‐up

Abstract

In the past 10 years, we have observed 112 cases of EDTA-dependent pseudothrombocytopenia (PTCP) due to in vitro platelet clumping at room temperature. 93 patients had antiplatelet antibodies (48 IgM, 30 IgG, 3 IgA, and 12 had two different isotypes concomitantly). In 20% of patients, the presence of IgM antibodies characteristically accompanied platelet agglutination also at 37 degrees C, and in citrated blood. The phenomenon was not age or sex related, nor was it associated with any particular pathology or use of specific drugs, and was present in both healthy subjects and patients with various diseases. Flow cytofluorimetric analysis of CD5-positive B cells, which are responsible for autoantibody production, did not demonstrate any changes in the percentage and absolute number of this lymphocyte subset. Average follow-up was 5 years (6 months-10 years); however, previous clinical records disclosed that PTCP was present for more than 15 years in four cases, and more than 20 years in three others, with no clinical manifestation of disease. This study confirms that EDTA-dependent PTCP is a phenomenon related to the presence of natural autoantibodies with antiplatelet activity, devoid of pathological significance. Its clinical interest resides in the need for its prompt and certain recognition in order to avoid unnecessary examinations and therapeutic interventions. The best and most rapid technique for obtaining accurate platelet counts in PTCP subjects is to collect and examine EDTA blood at 37 degrees C; however, clumping will still be present in about 20% of these cases, and even in citrated blood. To obviate this phenomenon, blood should be collected in ammonium oxalate, and platelets counted in a Burker chamber.

Effect of Anticoagulant and Storage Conditions on Platelet Size and Clumping in Healthy Dogs

“…Although platelet clumping usually results from activation of platelets during blood collection and handling, the tendency for a more pronounced platelet clumping at 4uC versus 25uC in the present study raises the possibility of an anticoagulantdependent, cold agglutinin-mediated platelet agglutination, which has been frequently documented in people and rarely in horses but is apparently rare or underestimated in dogs, or of a nonspecific cold activation of normal platelets. 1,10,22,24,36 In humans, EDTA-dependent platelet clumping is presumptively affected by agglutinating antibodies that recognize cytoadhesive receptors on platelet GPIIb-IIIa and/or by calcium chelation-triggered conformational changes in the cellular membrane. 2,17,18 Notably, in the present study, there was a significant variability of the frequency of platelet clumping among dogs, which accounted for 51% of the total variation.…”

Pseudo-Grey Platelet Syndrome: A Rare Artifact

“…Though there may be low platelet count and slight increase in MPV [4,6]. Much more common causes of the low counts of platelets that are often encountered on automated analyzers are due to partial clotting of the specimen, platelet satellitism [8] or anticoagulant-induced agglutination, mainly EDTA [9]. The platelet agglutination in the presence of EDTA is because of a reaction with circulating EDTA-sensitive antibodies.…”

“…Her initial CBC carried out in EDTA sample revealed Hb 10.8 mg/dl (10.1-12.3), RBC count 3.98 million/mm 3 (4.1-5.0), normal RBC indices, WBC count 24,100/mm 3 (6,000-18,000), with DLC comprising of N 12%, Eo 40% (AEC-9,640/mm 3 ), L 47%, M 0.1%. She had a platelet count of 2.02 lakhs/mm 3 and MPV was 12.1 fl (7)(8)(9)(10)(11). The microscopic examination of the PB smear confirmed eosinophilia but also revealed the presence of hardly visible platelets ( Fig.…”

Ethylenediaminetetraacetic Acid (EDTA)-Induced Thrombocytopenia: A Case Report

“…These antiplatelet antibodies, usually IgG or IgM, and rarely IgA, recognize platelet antigens on the platelet membrane modified by EDTA [10][11][12][13]. In contrast to serious and potential life-threatening causes of thrombocytopenia [14][15][16].…”

“…In contrast to serious and potential life-threatening causes of thrombocytopenia [14][15][16]. EDTA-PTCP is solely an in vitro effect without any clinical relevance [11]. Cation chelation by EDTA leads to a conformational change of the platelet membrane GPIIb-IIIa complex unmasking a cryptic epitope that becomes accessible for autoantibodies [17].…”