Indian Journal of Pathology and Microbiology

: 2023  |  Volume : 66  |  Issue : 1  |  Page : 227--228

EDTA dependent pseudo thrombocytopenia- A diagnostic dilemma!

Snigdha Goyal, Sunder Goyal 
 Consultant, District Hospital, Panchkula, Professor Surgery, ESI Medical College and Hospital, Faridabad, Haryana, India

Correspondence Address:
Snigdha Goyal
Consultant, District Hospital Panchkula, Sector 6, Panchkula - 134116, Haryana

How to cite this article:
Goyal S, Goyal S. EDTA dependent pseudo thrombocytopenia- A diagnostic dilemma!.Indian J Pathol Microbiol 2023;66:227-228

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Goyal S, Goyal S. EDTA dependent pseudo thrombocytopenia- A diagnostic dilemma!. Indian J Pathol Microbiol [serial online] 2023 [cited 2023 Mar 20 ];66:227-228
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Dear Editor,

Ethylenediamine tetra acetic acid (EDTA) dependent pseudo thrombocytopenia is a fairly rare phenomenon. The number of platelets counted by computerized cell counters is significantly lower than the real number of platelets in vivo. The occurrence is present in both healthy persons and patients with various diseases, and its incidence is about 0.09%–0.21%.[1] In pseudo thrombocytopenia (PTCP), platelet aggregation is in vitro, resulting in false reporting of a low platelet count by automatic platelets analyzers, classically EDTA-dependent.[2] Awareness of this phenomenon is important because PTCP may lead to the erroneous diagnosis of thrombocytopenia in a febrile patient leading to unnecessary and additional laboratory testing and inappropriate treatment.

We encountered an interesting and unique case of 16-year-old female, reported to the outpatient department of Civil Hospital Panchkula, with a history of fever for the last three days. There was no history of epistaxis, petechiae, ecchymosis or purpura. Ultrasonography revealed no organ enlargement. Routine investigations were performed. The initial CBC done using 5-part coulter showed relatively normal parameters except for an alarmingly low platelet count. On the first day, it was 37000 and gradually reduced to 11000 by day 4. [Figure 1] A peripheral smear (PBF) was subsequently prepared, which showed platelet aggregations with moderately giant platelets [Figure 2]. Family history, physical and systemic examination was normal. It was hypothesized that the low platelet count was due to EDTA-induced platelet aggregation. This was confirmed by examining a blood sample of the same patient with heparin as an anticoagulant which revealed normal platelet count, i.e., 3,20000. No aggregated platelets on the peripheral smear formed from the heparinized blood sample, as shown in [Figure 3].{Figure 1}{Figure 2}{Figure 3}

Pseudo thrombocytopenia or spurious thrombocytopenia can be a diagnostic dilemma as it can occur in several settings, all of which can be identified by reviewing the peripheral blood smear and/or repeating the CBC using a non-EDTA anticoagulant. EDTA is a commonly used anticoagulant in most blood samples in haematology laboratories as a calcium chelator. The EDTA is an ideal anticoagulant as it does not distort the morphology of blood cells. The aggregation of platelets in EDTA-dependent PTCP frequently is prohibited by other anticoagulants, such as sodium citrate or heparin.[3] The sample collection and blood examination at 37°C also avoid the aggregation of platelets.[4] In some cases, the aggregates are large enough to be counted as leukocytes by automated instruments, causing a concomitant pseudo leucocytosis. Pseudo thrombocytopenia has been associated with platelet cold agglutinins and multiple myeloma. Patients with conditions like malignancy, chronic liver disease, infection, pregnancy, autoimmune diseases, and cardiovascular diseases have a higher risk of EDTA-dependent PTCP.

The mechanism involves binding an antiplatelet autoantibody (IgG and IgM type) to the glycoprotein located on the cell membrane of platelets. The joint action of the chelating effect of EDTA on calcium ions and low temperature affects the platelet membrane glycoprotein complex IIb/IIIa. It reveals the epitope of glycoprotein IIb, which normally remains hidden in the glycoprotein complex IIb/IIIa.[5] When the autoantibody attaches to the epitope of glycoprotein IIb, platelet aggregation happens.[6]

Methods employed for distinguishing true thrombocytopenia from PTCP comprise using other anticoagulants (sodium citrate, oxalate, and heparin), stirring the temperature of a blood sample to 37°C, examining a blood sample containing EDTA as soon as possible and adding kanamycin or amikacin to a blood sample collected with EDTA.[7] Visual evaluation of blood smears is regarded as the gold standard for the detection of EDTA-PTCP.

Other probable pre-analytical aspects to be considered while examining platelet clumps are- the collection method, capillary, venous, or line draws. Capillary collections are prone to clotting and the formation of platelet clumps. Viral infection, drugs, and medications, particularly chemotherapeutic agents, are probable inducers of platelet clumping. In this case, we confirmed EDTA induced thrombocytopenia using a heparinized tube and a peripheral smear. In addition, we also observed a slight reduction in the leukocytes count.

When a patient with a low platelet count and without any haematological disorder, or bleeding tendency manifestation is identified, PTCP should also be considered. When EDTA-dependent PTCP is suspected, the patient's blood should be revaluated with another anticoagulant to rule out the possibility of spurious thrombocytopenia. Subsequently, an inexpensive, and diagnostic peripheral blood smear examination can be used to confirm platelet clumping.

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