A case of EDTA-dependent pseudothrombocytopenia: simple recognition of an underdiagnosed and misleading phenomenon

Ethylene Diamine Tetra Acetate-Induced Pseudo Thrombocytopenia (EDTA-PTCP) in an Adolescent: A Case Report

Ethylene diamine tetra acetate-induced pseudo thrombocytopenia (EDTA-PTCP) is a fictitious laboratory condition that is associated with platelet clumping, leading to falsely low platelet counts. This fictitious occurrence can lead to expensive, time-consuming, and invasive diagnostic procedures. It may also result in the application of unnecessary therapies, although it is not linked to any hemorrhagic symptoms or platelet malfunction. This emphasizes the necessity of verifying laboratory results from automated analyzers in every patient with thrombocytopenia with a peripheral smear, particularly when they are out of proportion when compared to the clinical features. When using hematology analyzers, EDTA-induced pseudo thrombocytopenia can be missed. In cases of isolated thrombocytopenia, this can be easily avoided by performing a simple visual peripheral blood smear check, hence making it an important differential for thrombocytopenia on an automatic analyzer report, which has to be ruled out. Here, we present the case of an adolescent who presented to us with low platelet counts and was diagnosed with EDTA-PTCP after proper evaluation.

Pseudothrombocytopenia, beyond a laboratory phenomenon: study of 192 cases

The platelet antibodies that cause pseudothrombocytopenia (PTCP) act only in vitro and do not produce clinical bleeding. Most studies on PTCP have focused on improving differential diagnosis with true thrombocytopenia but studies on the characteristics of patients with PTCP are limited. In this study, we aimed to evaluate the clinical and biological characteristics of 192 patients with PTCP. In addition to general variables, we evaluated automated and microscopic platelet counts, platelet clumps, platelet diameters, immature platelet fraction (IPF), and platelet antibodies. Adult women accounted for the largest subgroup of patients (n=82; 42.7%) and 67 patients (34.9%) were grouped into families. Forty-four patients (22.9%) had one or more associated autoimmune disorders (ADs); 39 relatives of these patients (19.8%) had ADs and 45 relatives (23.4%) had immune thrombocytopenia (ITP) or unspecified thrombocytopenia. Platelet cryptantibodies and/or autoantibodies were positive in 56 patients (30.1%). Most patients (n=169; 80%) had automated platelet counts >80×10⁹/L. In all patients, microscopic platelet counts were ≥150×10⁹/L. The platelet clump index (% increase in microscopic platelet count compared to automatic count) ranged from 30 to >7000%. Platelet diameters and IPF parameters were significantly greater in the PTCP versus healthy controls (p<0.001). A total of 17 patients (8.8%) had had previous ITP or the PTCP evolved into ITP. Our data suggest that PTCP should be considered a situation of autoimmunity; the assessment of platelet clumps has a high diagnostic value; the close association between ITP and PTCP suggests that these conditions could be different phases of the same process.

Pseudothrombocytopenia Inducing Nonindicated Platelet Transfusion after Cardiac Surgery

Pseudothrombocytopenia (PTCP) is an in vitro phenomenon of low platelet count caused by the agglutination of platelets, leading to false low platelet counts in automated cell counting. Typically, ethylenediaminetetraacetic acid (EDTA) mediates this platelet clumping. PTCP has little clinical significance, but misdiagnosis may lead to unnecessary diagnostic tests and treatment. In this case report, we present a 65-year-old Caucasian female suffering from multiple complications during and after cardiac surgery. During her postoperative stay at the ICU, she was diagnosed with thrombocytopenia and an inadequate response to platelet supplementation.

Pseudothrombocytopenia-A Review on Causes, Occurrence and Clinical Implications

Pseudothrombocytopenia (PTCP), a relative common finding in clinical laboratories, can lead to diagnostic errors, overtreatment, and further (even invasive) unnecessary testing. Clinical consequences with potential life-threatening events (e.g., unnecessary platelet transfusion, inappropriate treatment including splenectomy or corticosteroids) are still observed when PTCP is not readily detected. The phenomenon is even more complex when occurring with different anticoagulants. In this review we present a case of multi-anticoagulant PTCP, where we studied different parameters including temperature, amikacin supplementation, measurement methods, and type of anticoagulant. Prevalence, clinical risk factors, pre-analytical and analytical factors, along with clinical implications, will be discussed. The detection of an anticoagulant-dependent PTCP does not necessarily imply the presence of specific disorders. Conversely, the incidence of PTCP seems higher in patients receiving low molecular weight heparin, during hospitalization, or in men aged 50 years or older. New analytical technologies, such as fluorescence or optical platelet counting, will be soon overturning traditional algorithms and represent valuable diagnostic aids. A practical laboratory approach, based on current knowledge of PTCP, is finally proposed for overcoming spuriously low platelet counts.

Pan-Pseudothrombocytopenia in COVID-19: A Harbinger for Lethal Arterial Thrombosis?

Pseudothrombocytopenia in the setting of COVID-19-associated coagulopathy prompts the question whether it is representative of increased platelet aggregation activity in vivo.

Pseudothrombocytopenia: a case of platelet satellitism and phagocytosis by neutrophils

Thrombocytopenia is a clinically important condition that can lead to several problems when not correctly diagnosed. A decrease of platelet counts due to an in vitro phenomenon, Pseudothrombocytopenia, can be misunderstood and unnecessarily treated. The present case study describes a 57-year-old male with a history of pancreas adenocarcinoma and a current Staphylococcus aureus infection without any signs or symptoms that could explain the low levels of platelets obtained after blood analysis. Blood smear evaluation detected both platelet satellitism and phagocytosis by neutrophils. As this sample was anticoagulated with ethylenediaminetetraacetic acid (EDTA), a new blood sample with citrate was analyzed. Platelet count was normal and no morphological abnormalities were detected. This case emphasizes the need for considering not only laboratory results but also the patient clinical information to guarantee the correct diagnosis and the best treatment possible.

Platelet Disorders

After vascular injury and exposure of subendothelial matrix proteins to the intravascular space, mediators of hemostasis are triggered and allow for clot formation and restoration of vascular integrity. Platelets are the mediators of primary hemostasis, creating a platelet plug and allowing for initial cessation of bleeding. Platelet disorders, qualitative and quantitative, may result in bleeding signs and symptoms, particularly mucocutaneous bleeding such as epistaxis, bruising, petechiae, and heavy menstrual bleeding. Increasing evidence suggests that platelets have functional capabilities beyond hemostasis, but this review focuses solely on platelet hemostatic properties. Herein, normal platelet function as well as the effects of abnormal function and thrombocytopenia are reviewed.

A Curious Case of Pseudothrombocytopenia due to In Vitro Agglutination

Pseudothrombocytopenia (PTCP) is a laboratory phenomenon that can occur in hospitalized patients, with approximately 0.1 to 0.2% due to ethylenediaminetetraacetic acid (ETDA). The EDTA-dependent mechanism of PTCP occurs due to a conformational change of platelet surface glycoprotein IIb/IIIa (GPIIb/IIIa) caused by EDTA, which allows natural IgM or IgG auto-antibodies to bind to GPIIb/IIIa, leading to platelet agglutination. In most cases, PTCP resolves when a repeat blood sample is drawn in collection tubes containing either citrate or heparin. Here, we report a case of a 23-year-old female presenting with symptoms of gastroenteritis. She exhibited PTCP with blood draws obtained in not only collection tubes containing ETDA, but also with collection tubes containing heparin and citrate, which is highly unusual. The lack of resolution of platelet clumping in collection tubes containing either heparin or citrate suggests that heparin or citrate may also cause conformational changes to platelet surface glycoproteins in a similar mechanism as that of EDTA that allows binding of certain auto-antibodies.

Thrombocytopenia associated with clonidine in a case of clozapine-induced sialorrhea

Clozapine is approved by the US Food and Drug Administration for treatment-resistant schizophrenia and mitigation of suicidality in patients with schizophrenia or schizoaffective disorder. Clozapine requires monitoring of adverse events, such as hypotension, myocarditis, cardiomyopathy, seizures, severe neutropenia, and gastrointestinal hypomotility. Sialorrhea is another adverse event that can be bothersome for patients and result in nonadherence or the development of aspiration pneumonia. Clonidine, an α_2A adrenergic receptor agonist, is one medication option that can reduce or eliminate sialorrhea. Clonidine is generally well tolerated but can contribute to hypotension and sedation. One adverse event associated with clonidine not described in the literature is thrombocytopenia. Reported is a case of clonidine-associated thrombocytopenia when used for the treatment of clozapine-induced sialorrhea.

Mindray SF-Cube technology: An effective way for correcting platelet count in individuals with EDTA dependent pseudo thrombocytopenia

Several strategies are applied to determine the precise platelet count in individuals with ethylenediaminetetraacetic acid dependent pseudo thrombocytopenia (EDTA-PTCP) caused by in vitro aggregation of platelets in daily laboratory practice. None of them proves optimal for routine purposes. Thus, Mindray has developed the SF-Cube technology coupled with the CDR mode in the Mindray hematology analyzer to overcome the problem of EDTA-PTCP. With Mindray SF-Cube technology, platelet aggregates dissociate effectively and platelets are correctly counted in the CDR mode without pre-analytical management. In our studies, the EDTA-PTCP blood samples when analyzed with the CDR mode of Mindray BC-6800 plus analyzer, yield a markedly higher platelet count compared to those obtained with PLT-I on Sysmex XN-9000 hematology analyzer. We conclude that in patients with known or suspected EDTA-PTCP Mindray SF-Cube technology is a straightforward and effective way of determining the platelet count in EDTA-anticoagulated blood.

Pseudothrombocytopenia in Patients with Scrub Typhus Infection

Pseudothrombocytopenia is an ex vivo EDTA-dependent artefactual thrombocytopenia, that has been described in association with several conditions. When EDTA-blood samples are drawn from patients with pseudothrombocytopenia and analysed by automated cell counters, low platelet counts are obtained (often below 50,000/mm³). However, simultaneous heparinised samples show normal platelet counts, and peripheral smears show no reduction in numbers of platelets. We report a series of 12 patients with scrub typhus infections and pseudothrombocytopenia. An association between these two entities has only recently been appreciated. It appears that pseudothrombocytopenia may sometimes accompany acute scrub typhus infections. The distinction between pseudothrombocytopenia and true thrombocytopenia is of great clinical relevance, as the former is merely a laboratory artefact, and does not require blood product transfusions despite apparently severe reductions in platelet counts. It is therefore important to recognise that apparent thrombocytopenia, especially in patients with an acute febrile illness due to scrub typhus, is not always true thrombocytopenia.

Harmonization of interpretative comments in laboratory hematology reporting: the recommendations of the Working Group on Diagnostic Hematology of the Italian Society of Clinical Chemistry and Clinical Molecular Biology (WGDH-SIBioC)

The goal of harmonizing laboratory testing is contributing to improving the quality of patient care and ultimately ameliorating patient outcome. The complete blood and leukocyte differential counts are among the most frequently requested clinical laboratory tests. The morphological assessment of peripheral blood cells (PB) through microscopic examination of properly stained blood smears is still considered a hallmark of laboratory hematology. Nevertheless, a variable inter-observer experience and the different terminology used for characterizing cellular abnormalities both contribute to the current lack of harmonization in blood smear revision. In 2014, the Working Group on Diagnostic Hematology of the Italian Society of Clinical Chemistry and Clinical Molecular Biology (WGDH-SIBioC) conducted a national survey, collecting responses from 78 different Italian laboratories. The results of this survey highlighted a lack of harmonization of interpretative comments in hematology, which prompted the WGDH-SIBioC to develop a project on “Harmonization of interpretative comments in the laboratory hematology report”, aimed at identifying appropriate comments and proposing a standardized reporting system. The comments were then revised and updated according to the 2016 revision of the World Health Organization classification of hematologic malignancies. In 2016, the Working Group on Diagnostic Hematology of the Italian Society of Clinical Chemistry and Clinical Molecular Biology (WGDH SIBioC) published its first consensus based recommendation for interpretative comments in laboratory hematology reporting whit the purpose of evaluating comments and the aim to (a) reducing their overall number, (b) standardizing the language, (c) providing information that could be easily comprehended by clinicians and patients, (d) increasing the quality of the clinical information, and (e) suggesting additional diagnostic tests when necessary. This paper represents a review of the recommendations of the former document.

Effect of time and temperature on anticoagulant-dependent pseudothrombocytopenia in Göttingen minipigs

BACKGROUND

A marked decrease in thrombocyte count was observed between subsequent measurements of the same EDTA blood sample in several minipigs, but little information was available explaining this finding.

OBJECTIVES

The objective was to evaluate the impact of several preanalytic variables on thrombocyte counts in minipigs, in order to improve understanding of the in vitro thrombocyte decrease observed.

MATERIALS AND METHODS

Hematology blood samples from male and female Göttingen minipigs were collected using EDTA or citrate as an anticoagulant. Samples were stored under different conditions (room temperature, 4°C, or 37-38°C) and were analyzed approximately 0.5 to one h, 3.5-4 h, 7-7.5 h, and 28-29 h after collection.

RESULTS

In EDTA blood samples from male minipigs stored at room temperature, there was a progressive thrombocyte decrease over time up to -71% after 29 h, caused by in vitro aggregation. In females, no consistent change was seen up to 7.5 h, but there was a decrease up to -47% after 29 h. Thrombocyte count was most stable during storage at 4°C. No consistent marked decrease in thrombocyte counts was seen for citrated blood at room temperature, although such a decrease was present in a few individual animals.

CONCLUSIONS

Study results provide evidence for an anticoagulant-dependent pseudothrombocytopenia in minipigs progressing over time and depending on the storage temperature of the blood sample. It is therefore recommended to perform thrombocyte counts as soon as possible after blood collection, and in case of low counts, investigate for the presence of artifactual platelet clumping.

Transient appearance of EDTA-dependent pseudothrombocytopenia in a postoperative patient with sepsis: A case report

RATIONALE

Ethylenediaminetetraacetic acid-dependent pseudothrombocytopenia (EDTA-PTCP) is a rare phenomenon characterized by spuriously low platelet counts when EDTA reacts with harvested blood. However, to the best of our knowledge, only two cases involving EDTA-PTCP in postoperative patients with sepsis have been reported. Here, we describe a case of EDTA-PTCP that appeared transiently in a postoperative patient with sepsis.

PATIENT CONCERNS

A 68-year-old female patient underwent laparoscopic tension-free hernioplasty for incisional hernia. Postoperatively, the patient developed very low platelet counts. The number of platelets in this patient had not improved following treatment with fresh-frozen plasma and platelet transfusions.

DIAGNOSES

The diagnosis of EDTA-PTCP was confirmed from the discovery of platelet aggregation in peripheral blood smears.

INTERVENTIONS

We used sodium citrate-anticoagulated blood samples for platelet counting.

OUTCOMES

The patient's platelet counts returned to normal with the use of sodium citrate-anticoagulated blood samples. Furthermore, the phenomenon of EDTA-PTCP disappeared when the patient was cured.

LESSONS

The phenomenon of low platelet counts in postoperative patients with sepsis should be considered as possible EDTA-PTCP. In addition, peripheral blood smears and the use of sodium citrate anticoagulant are effective and valuable methods that can help identify EDTA-PTCP.

Pseudothrombocytopenia due to Platelet Clumping: A Case Report and Brief Review of the Literature

Platelet clumping is a common laboratory phenomenon that complicates or precludes reporting of platelet count. It is often, but not always, a phenomenon commonly caused by the anticoagulant EDTA. Herein, we discuss a case of a 14-year-old girl who was found to have platelet clumping and discuss the work-up she underwent to investigate her pseudothrombocytopenia.

Towards Clinical Applications of Blood-Borne miRNA Signatures: The Influence of the Anticoagulant EDTA on miRNA Abundance

Background

Circulating microRNAs (miRNAs) from blood are increasingly recognized as biomarker candidates for human diseases. Clinical routine settings frequently include blood sampling in tubes with EDTA as anticoagulant without considering the influence of phlebotomy on the overall miRNA expression pattern. We collected blood samples from six healthy individuals each in an EDTA blood collection tube. Subsequently, the blood was transferred into PAXgene^TM tubes at three different time points, i.e. directly (0 min), 10 min, and 2 h after phlebotomy. As control blood was also directly collected in PAXgene^TM blood RNA tubes that contain a reagent to directly lyse blood cells and stabilize their content. For all six blood donors at the four conditions (24 samples) we analyzed the abundance of 1,205 miRNAs by human Agilent miRNA V16 microarrays.

Results

While we found generally a homogenous pattern of the miRNA abundance in all 24 samples, the duration of the EDTA treatment appears to influence the miRNA abundance of specific miRNAs. The most significant changes are observed after longer EDTA exposition. Overall, the impact of the different blood sample conditions on the miRNA pattern was substantially lower than intra-individual variations. While samples belonging to one of the six individuals mostly cluster together, there was no comparable clustering for any of the four tested blood sampling conditions. The most affected miRNA was miR-769-3p that was not detected in any of the six PAXgene blood samples, but in all EDTA 2h samples. Accordingly, hsa-miR-769-3p was also the only miRNA that showed a significantly different abundance between the 4 blood sample conditions by an ANOVA analysis (Benjamini-Hochberg adjusted p-value of 0.003). Validation by qRT-PCR confirmed this finding.

Conclusion

The pattern of blood-borne miRNA abundance is rather homogenous between the four tested blood sample conditions of six blood donors. There was a clustering between the miRNA profiles that belong to a specific blood donor, but not between any of the four tested blood sampling conditions. The results show a limited overall impact of the blood sampling conditions on the miRNA pattern. Notwithstanding, the abundance of single miRNAs can be significantly altered by different blood sampling conditions.

Autoimmune Thrombocytopenia Complicated by EDTA- and/or Citrate-Dependent Pseudothrombocytopenia

Background

Pseudothrombocytopenia (PTCP) is a well-known phenomenon. However, confusion may occur due to unusual characteristics.

Case Reports

Two patients with autoimmune thrombocytopenia (ITP) and long-lasting PTCP are described. Initially, only the diagnosis of ITP was confirmed. During observation, discrepancies were recognized between clinical findings and platelet counts. Re-examination resulted in the additional diagnosis of EDTA-dependent PTCP. Subsequently, the latter diagnosis was changed to citrate-dependent PTCP in both cases. Interestingly, PTCP was observed to change again and became recognizable in citrate or heparin, and only during the first 20-30 min following phlebotomy in EDTA specimens.

Conclusion

The incidence of concomitant ITP with PTCP might be higher than previously reported, and PTCP may have variable dynamics and characteristics.

An atypical IgM class platelet cold agglutinin induces GPVI-dependent aggregation of human platelets

Platelet cold agglutinins (PCA) cause pseudothrombocytopenia, spurious thrombocytopenia due to ex vivo platelet clumping, complicating clinical diagnosis, but mechanisms and consequences of PCA are not well defined. Here, we characterised an atypical immunoglobulin (Ig)M PCA in a 37-year-old woman with lifelong bleeding and chronic moderate thrombocytopenia, that induces activation and aggregation of autologous or allogeneic platelets via interaction with platelet glycoprotein (GP)VI. Patient temperature-dependent pseudothrombocytopenia was EDTA-independent, but was prevented by integrin αIIbβ3 blockade. Unstimulated patient platelets revealed elevated levels of bound IgM, increased expression of activation markers (P-selectin and CD63), low GPVI levels and abnormally high thromboxane (TX)A2 production. Patient serum induced temperature- and αIIbβ3-dependent decrease of platelet count in allogeneic donor citrated platelet-rich plasma (PRP), but not in PRP from Glanzmann's thrombasthenia or afibrinogenaemia patients. In allogeneic platelets, patient plasma induced shape change, P-selectin and CD63 expression, (14)C-serotonin release, and TXA2 production. Activation was not inhibited by aspirin, cangrelor or blocking anti-Fc receptor (FcγRIIA) antibody, but was abrogated by inhibitors of Src and Syk, and by a soluble GPVI-Fc fusion protein. GPVI-deficient platelets were not activated by patient plasma. These data provide the first evidence for an IgM PCA causing platelet activation/aggregation via GPVI. The PCA activity persisted over a five-year follow-up period, supporting a causative role in patient chronic thrombocytopenia and bleeding.

Poorer prognosis with ethylenediaminetetraacetic acid-dependent pseudothrombocytopenia: a single-center case-control study

In ethylenediaminetetraacetic acid (EDTA)-dependent pseudothrombocytopenia (PTCP), automated platelet counts are lower than actual counts because of EDTA-induced aggregation. Factors contributing to the incidence of EDTA-PTCP are unknown, and no study has assessed the prognosis of EDTA-PTCP patients. This retrospective study assessed characteristics in EDTA-PTCP patients and matched controls to determine differences in prognosis. A retrospective case-control study was designed. From the University of Tokyo Hospital database, we identified patients diagnosed with EDTA-PTCP between 2009 and 2012, and performed 1:2 case:control matching for age and sex. A control group of sex- and age-matched patients was selected at random from the same database. We investigated differences in the frequency of complications, medication history, and blood transfusion history between the groups at the time of blood collection. Prognosis was evaluated using multivariate Cox regression analysis adjusting for age, sex, autoimmune disease, liver disease, and malignant tumor. We identified 104 EDTA-PTCP patients and 208 matched controls. The median age was 69.0 years (interquartile range: 54-76), with men comprising 51%. EDTA-PTCP patients had a higher frequency of malignant tumor and a lower frequency of hypertension and diabetes than controls. After adjustment for background factors, prognosis of EDTA-PTCP patients was significantly poorer than controls (hazard ratio, 11.8; 95% confidence intervals, 2.62-53.54). In conclusion, EDTA-PTCP patients had higher mortality, and EDTA-PTCP may need to be recognized as an indicator of worse prognosis.