Pseudothrombocytopenia in plateletpheresis donors

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.

EDTA-induced pseudothrombocytopenia in hematopoietic stem cell donor

We herein report a case of peripheral blood stem cell transplantation (PBSCT) involving a donor with EDTA-induced pseudothrombocytopenia (PTCP). The apheresis product was inspected for 24 h and there was no platelet clumping or thrombocytopenia. In the first 14 months after PBSCT, there has been no transfer of PTCP symptoms.

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.

[A non-EDTA-dependent pseudothrombocytopenia: about a case]

La pseudothrombopénie est un phénomène rare de laboratoire, expliquée par une agglutination in vitro des plaquettes. L’examen au microscope du frottis du sang périphérique est un examen clé, pour confirmer le diagnostic et pour éviter toute décision clinique et thérapeutique inadaptée voir dangereuse. Sa survenue chez un patient, sous traitement par l’héparine, pose le problème de diagnostic différentiel avec la thrombopénie héparino-induite. Notre objective, à travers cette observation, est d’éviter toute confusion entre ce phénomène purement artéfactuel et la thrombopénie héparino-induite.

Thrombocytopenia and Critical Care Medicine

Platelet transfusions play an important role in the treatment of critically ill patients. Like any blood component, however, there are various aspects of platelet transfusion therapy that need be considered by the intensivist. These include the proper dose and type of platelet component to infuse, as well as the route and method of administration. Methods to reduce the volume of the transfused platelets, for example, must ensure that the infused platelets will be functional and viable, posttransfusion. Treatment and diagnosis of the HLA alloimmunized recipient can pose a serious challenge to the clinician and an obstacle to adequate platelet therapy. An ICU patient for whom an adequate posttransfusion platelet increment cannot be achieved is at great risk of suffering a fatal hemorrhage. The ICU physician should be aware of the techniques used in modern transfusion practice to avoid having to deal with this complication. Adverse reactions to platelet transfusion include not only serologic ones, but those related to febrile and allergic complications, as well as infectious complications. The latter group includes diseases caused by infection with cytomegalovirus, bacteria, and a cadre of viruses including HIV and hepatitis. The clinical approach to thrombocytopenia in the ICU will be covered in some detail in an effort to review many of the conditions associated with recipient thrombocytopenia, including ITP, TTP, dilutional thrombocytopenia, DIC, surgery, HELLP syndrome, and drug-induced thrombocytopenia. Unfortunately the treatment approaches traditionally used are not always derived from evidence-based studies. This review covers many of these topics in an attempt to help physicians become better able to manage thrombocytopenia in the ICU and thus provide the best transfusion therapy for their patients.

Pseudothrombocytopenia: A Rare Phenomenon

Thrombocytopenia is a serious situation that causes anxiety in doctors and patients due to its relationship with serious hemorrhagic manifestations. Pseudothrombocytopenia, however, is a situation without clinical interest because it is an in vitro decrease in platelet count. Pseudothrombocytopenia is related to the ethylenediaminetetraacetate (EDTA)-dependent exposure of antigenic determinants of platelet membrane gly coproteins gpIIb-IIIa and the subsequent reaction of common antibodies with these receptors. To our knowledge, a similar situation in Greece has not been reported. The main character istic of pseudothrombocytopenia due to EDTA is that the fall in platelet count is time-dependent and it disappears after the use of anticoagulant other than EDTA (e.g., citrate sodium or hep arin). We present seven cases of pseudothrombocytopenia re vealed when we used automatic hematologic analyzers and EDTA as an anticoagulant. After the use of another anticoagu lant (e.g., citrate sodium) the platelet count in the same hema tologic analyzer was normal.

Discovery and Correction of Spurious Low Platelet Counts due to EDTA-Dependent Pseudothrombocytopenia

BACKGROUND

Ethylene diamine tetraacetic acid dependent pseudothrombocytopenia (EDTA-PTCP) is a laboratory artifact that may lead to unnecessary evaluation and treatment of patients. The purpose of this article is to discuss how to identify EDTA-PTCP and correct spurious low platelet counts in clinical laboratories.

METHODS

We use two criteria to screen for platelet aggregation: (1) an abnormal platelet count in EDTA-treated blood from a patient lacking clinical signs of a platelet disorder, and (2) an instrument flag for platelet clumps. EDTA-PTCP was confirmed by microscopic examination for platelet agglutination and by platelet counts that corrected with citrate sample. In addition, the time course of EDTA-PTCP was investigated in samples from 26 patients anticoagulated with EDTA-K2 and sodium citrate. Amikacin (5 mg/ml) was added to tubes with EDTA-K2 or sodium citrate from seven additional cases in order to confirm its dissociative effect on platelet aggregation.

RESULTS

In our laboratory, the overall incidence of EDTA-PTCP was approximately 0.09%; and the duration was between 2 weeks and 6 months. EDTA-PTCP was time-dependent and occurred as early as 10 min after sample collection. Weaker agglutination could also occur in most corresponding citrate-treated samples. The dissociative effect of amikacin on platelet agglutination was case-specific and not concentration-dependent.

CONCLUSIONS

The method of screening for platelet clumping with the help of XE5000 images is convenient. The decline in the platelet count is related to the length of time and the intensity of chelation. Amikacin supplement is not always effective for correcting platelet counts in vitro.

Effective estimation of correct platelet counts in pseudothrombocytopenia using an alternative anticoagulant based on magnesium salt

Pseudothrombocytopenia remains a challenge in the haematological laboratory. The pre-analytical problem that platelets tend to easily aggregate in vitro, giving rise to lower platelet counts, has been known since ethylenediamine-tetra acetic acid EDTA and automated platelet counting procedures were introduced in the haematological laboratory. Different approaches to avoid the time and temperature dependent in vitro aggregation of platelets in the presence of EDTA were tested, but none of them proved optimal for routine purposes. Patients with unexpectedly low platelet counts or flagged for suspected aggregates, were selected and smears were examined for platelet aggregates. In these cases patients were asked to consent to the drawing of an additional sample of blood anti-coagulated with a magnesium additive. Magnesium was used in the beginning of the last century as anticoagulant for microscopic platelet counts. Using this approach, we documented 44 patients with pseudothrombocytopenia. In all cases, platelet counts were markedly higher in samples anti-coagulated with the magnesium containing anticoagulant when compared to EDTA-anticoagulated blood samples. We conclude that in patients with known or suspected pseudothrombocytopenia the magnesium-anticoagulant blood samples may be recommended for platelet counting.

Does my patient have a life- or limb-threatening thrombocytopenia?

The diagnosis and management of severe thrombocytopenias can be difficult, but is necessary to avoid significant morbidity and mortality. The causes of severe thrombocytopenias, often with a platelet count of less than 10 × 10(9)/L, include heparin-induced thrombocytopenia, the thrombotic microangiopathies, the catastrophic antiphospholipid syndrome, preeclampsia/HELLP, and posttransfusion purpura. This review provides a brief overview of the key clinical features of each of these major clinical entities, and strategies for their diagnostic workup and therapeutic management.

Amikacin can be added to blood to reduce the fall in platelet count

Our objective was to develop an effective method to prevent the fall in platelet count for patients with anticoagulant-dependent (AD) pseudothrombocytopenia, a spurious phenomenon due to anticoagulant-induced aggregation of platelets. We report a case of insidious multianticoagulant-dependent pseudothrombocytopenia in which AD pseudothrombocytopenia may be caused by 4 anticoagulants, eg, EDTA, sodium citrate, heparin, and sodium fluoride (NaF). Multianticoagulant-dependent pseudothrombocytopenia was confirmed by finding clumped platelets on microscopic evaluation in 4 anticoagulated blood samples. With this case, we tried a variety of reagents, including aminoglycosides, eg, gentamicin and amikacin, vitamin B(6), and aminophylline to inhibit pseudothrombocytopenia. Except for amikacin, all reagents failed to prevent pseudothrombocytopenia. Microscopic examination of K(2)-EDTA-, heparin-, sodium citrate-, and NaF-anticoagulated blood samples showed massive platelet clumping, but no aggregate was seen in the anticoagulated blood with amikacin. When amikacin was added within 1 hour after blood sample withdrawal, platelet, WBC, and RBC counts and hemoglobin level, mean corpuscular volume, and mean platelet volume remained unchanged for up to 4 hours at room temperature. These findings suggest that amikacin could inhibit and dissociate pseudo platelet aggregation in multianticoagulant-dependent pseudothrombocytopenia and EDTA-induced pseudothrombocytopenia.

Prevalence and course of pseudothrombocytopenia in outpatients

BACKGROUND

The prevalence and course of pseudothrombocytopenia in outpatients is uncertain.

METHODS

In a cohort study of 687,955 members of a health maintenance organization, we extracted 36,780 consecutive automated complete blood count test results and determined the point prevalence of pseudothrombocytopenia during a one-month period. We also calculated a retrospective cumulative prevalence over the past 5 years.

RESULTS

There were 1105 (2.7%) patients with platelet counts of 100-149×10(9)/L and 304 (0.8%) with counts <100×10(9)/L, of whom 12.8% (n=39) had pseudothrombocytopenia newly discovered or in the past. There were 40 additional patients with a history of pseudothrombocytopenia, but now showing platelet counts of 150×10(9)/L or more, and another 21 with platelet counts of 100-149×10(9)/L. The total cumulative prevalence of pseudothrombocytopenia was 0.27% (100/36,780), 2.5-fold higher than the point prevalence of 0.11% (39/36,780). Platelet counts were extremely variable in these patients during the 5-year follow-up period.

CONCLUSIONS

Physicians should be aware of the variability of platelet counts in patients with pseudothrombocytopenia in order to reduce unnecessary retesting. Since pseudothrombocytopenia can result in platelet counts between 100 and 149×10(9)/L, peripheral smears should be done in all patients with such values, or the reference limit value should be lowered to 100×10(9)/L.

Spurious counts and spurious results on haematology analysers: a review. Part I: platelets

The widespread use of haematology analysers (HA) has led to a major improvement of cellular haematology, because of quick and accurate results found in most instances. However, in several situations, spurious results are observed. Inadequate blood samples, situations induced by the anticoagulant(s) used, peculiar changes related to the pathology in the patient, and technical considerations about performances of the various HA must be considered. Spurious thrombocytopenia occurs in several circumstances related to the presence of ethylenediamine tetra-acetic acid (EDTA) used as the anticoagulant. Mechanism of EDTA-dependent platelet (PLT) agglutination is related to circulating (auto)antibodies directed against normally hidden epitope(s) in the glycoprotein alpha IIb/beta IIIa complex from PLT membrane exposed only in the presence of EDTA. Other spuriously low PLT counts may be related to EDTA, including PLT rosetting around white blood cells (WBC; satellitism) and PLT-WBC aggregates, but mechanisms responsible for those latter phenomena are less well known. Spurious increase of PLT count may be related to several situations, including fragmented red blood cells, cytoplasmic fragments of nucleated cells, cryoglobulins, bacteria or fungi, and lipids. Flags generated in several of these situations alert the operator on possible abnormal findings and may identify the problem. Analysing only PLT parameters is not sufficient: in many situations the WBC differential scattergram is of crucial help for flagging. Flags generated depend on the software version on the HA used, the performance in detecting the same anomalies may differ according to which analyser is used, even those from the same manufacturer. Operators must be aware of the characteristics of their analyser and be able to recognize and circumvent anomalous results.

Artifacts that may be present on a blood film

Many artifacts or pseudoartifacts may be noted during the examination of a blood film. Artifactual results also may be generated by automated hematology analyzers, which in turn may be investigated by blood film examination. Some artifacts are misdiagnosed, and this in turn leads to inappropriate investigations or treatment. An awareness of the spectrum of spurious or artifactual results may help to prevent such an unfortunate occurrence.

Volunteer donor apheresis

Volunteer donor apheresis has evolved from early plasmapheresis procedures that collected single components into technically advanced multicomponent procedures that can produce combinations of red blood cells, platelets, and plasma units. Blood collection and utilization is increasing annually in the United States. The number of apheresis procedures is also increasing such that single donor platelet transfusions now exceed platelet concentrates from random donors. Donor qualifications for apheresis vary from those of whole blood. Depending on the procedure, the donor weight, donation interval, and platelet count must be taken into consideration. Adverse effects of apheresis are well known and fortunately occur in only a very small percentage of donors. The recruitment of volunteer donors is one of the most challenging aspects of a successful apheresis program. As multicomponent apheresis becomes more commonplace, it is important for collection centers to analyze the best methods to recruit and collect donors.

Occurrence and clinical significance of pseudothrombocytopenia during abciximab therapy

OBJECTIVES

This study determined the incidence of pseudothrombocytopenia during abciximab therapy administered for percutaneous coronary interventions and compared the clinical course of patients with pseudothrombocytopenia with the clinical courses of patients with thrombocytopenia and patients with normal platelet counts.

BACKGROUND

Although pseudothrombocytopenia has been previously reported during therapy with abciximab, the incidence and significance of this occurrence are unknown. The failure to differentiate pseudothrombocytopenia from thrombocytopenia could lead to unnecessary interruption of abciximab infusions or to platelet transfusions.

METHODS

The incidences of pseudothrombocytopenia and thrombocytopenia were determined in four large placebo-controlled abciximab trials: c7E3 Fab Antiplatelet Therapy in Unstable Refractory Angina (CAPTURE), Evaluation of 7E3 for the Prevention of Ischemic Complications (EPIC), Evaluation of Percutaneous Transluminal Coronary Angioplasty to Improve Long-term Outcome of c7E3 GpIIb/IIIa Receptor Blockade (EPILOG) and Evaluation of Platelet IIb/IIIa Inhibitor for Stenting (EPISTENT). The clinical features, bleeding complications and major clinical outcomes of patients with pseudothrombocytopenia and those with thrombocytopenia were compared with each other and with those of patients with normal platelet count.

RESULTS

Pseudothrombocytopenia occurred in 2.1% (95% confidence intervals [CI]: 1.7%, 2.5%) of abciximab-treated patients and in 0.6% of placebo-treated patients (p < 0.001). Thrombocytopenia occurred in 3.7% (95% CI: 3.2%, 4.2%) of abciximab-treated patients and in 1.8% (95% CI: 1.3%, 2.3%) of placebo-treated patients (p < 0.001). Patients with thrombocytopenia had significantly higher rates of major bleeding, major decreases in hemoglobin and increased transfusion requirements of both blood and platelets compared with those without thrombocytopenia. By contrast, pseudothrombocytopenic patients did not differ from patients with normal platelet counts in any of the measures of blood loss or transfusion requirements. Thrombocytopenic patients, but not those with pseudothrombocytopenia, had increased rates of revascularization at 30 days and six months. As previously reported, there was also a higher rate of death and myocardial infarction in the thrombocytopenic patients.

CONCLUSIONS

Pseudothrombocytopenia is the cause of more than one third (36.3%) of low platelet counts in patients undergoing coronary interventions who are treated with abciximab. This study demonstrates that pseudothrombocytopenia is a benign laboratory condition that does not increase bleeding, stroke, transfusion requirements or the need for repeat revascularization. It is important to recognize pseudothrombocytopenia so that the beneficial effects of abciximab are not lost by premature termination of therapy.

Drug-induced thrombocytopenia

Many drugs can induce thrombocytopenia mediated by drug-dependent antiplatelet antibodies. Recent studies have documented specific epitopes for drug-dependent antibody binding on glycoprotein Ib-IX, glycoprotein IIb-IIIa, and platelet-endothelial cell adhesion molecule-1. Molecular identification of antibody binding sites may help to identify susceptible individuals. Management of patients with unexpected thrombocytopenia who are taking multiple drugs remains a difficult clinical problem. A recent systematic review of all published case reports of drug-induced thrombocytopenia ranks drugs according to the strength of clinical evidence for a causal relation to thrombocytopenia. This database is available online at http://moon.ouhsc.edu/jgeorge.