LGCmain
Indian Journal of Pathology and Microbiology
Home About us Instructions Submission Subscribe Advertise Contact e-Alerts Ahead Of Print Login 
Users Online: 2014
Print this page  Email this page Bookmark this page Small font sizeDefault font sizeIncrease font size


 
  Table of Contents    
CASE REPORT  
Year : 2013  |  Volume : 56  |  Issue : 3  |  Page : 306-308
Pseudothrombocytopenia observed with ethylene diamine tetra acetate and citrate anticoagulants, resolved using 37°C incubation and Kanamycin


1 Department of Transfusion Medicine and Immunohaematology, Christian Medical College, Vellore, Tamil Nadu, India
2 Department of Pathology, Christian Medical College, Vellore, Tamil Nadu, India

Click here for correspondence address and email

Date of Web Publication24-Oct-2013
 

   Abstract 

Pseudothrombocytopenia (PTP) is defined by falsely low platelet counts on automated analyzers caused by in vitro phenomena including large platelet aggregates in blood samples. Diagnosis and resolution of PTP is crucial as it can lead to unwarranted interventions. We discuss a case of PTP in a pre-surgical setting, which was resolved using 37°C incubation and Kanamycin.

Keywords: Kanamycin, platelet aggregates, pseudothrombocytopenia

How to cite this article:
Kamath V, Sarda P, Chacko MP, Sitaram U. Pseudothrombocytopenia observed with ethylene diamine tetra acetate and citrate anticoagulants, resolved using 37°C incubation and Kanamycin . Indian J Pathol Microbiol 2013;56:306-8

How to cite this URL:
Kamath V, Sarda P, Chacko MP, Sitaram U. Pseudothrombocytopenia observed with ethylene diamine tetra acetate and citrate anticoagulants, resolved using 37°C incubation and Kanamycin . Indian J Pathol Microbiol [serial online] 2013 [cited 2020 Feb 19];56:306-8. Available from: http://www.ijpmonline.org/text.asp?2013/56/3/306/120407



   Introduction Top


Pseudothrombocytopenia (PTP) is defined by falsely low platelet counts on automated analyzers and is caused by in vitro phenomena including large platelet aggregates in blood samples. Platelet aggregates on account of their large size are frequently not included in the platelet window of auto-analyzers, but are counted as leukocytes, leading to misleadingly low platelet counts and high leukocyte counts. The phenomenon can be suspected on examining the platelet histogram and review of the smear should confirm the presence of aggregates.

Far from being a harmless curiosity, undiagnosed PTP is a pitfall leading to unwarranted investigations, platelet transfusions and treatment with glucocorticoids. In a pre-surgical setting, it can be a nuisance as the platelet aggregation interferes with accurate platelet counts, leading to the conundrum of whether to support with platelet transfusions or not.

Here, we recount how a case of PTP diagnosed in a patient with an intracranial hematoma requiring evacuation, was resolved using 37°C incubation and Kanamycin.


   Case Report Top


A 76-year-old male patient presented with a non-traumatic frontoparietal subdural hematoma and was posted for evacuation. He had a past history of hematochezia and epistaxis, during the investigation of which, he had been diagnosed to have thrombocytopenia and had received a platelet transfusion elsewhere. In addition, he was diabetic and hypertensive and on medication for the same. He had been on aspirin, but discontinued it a year previously.

Repeated pre-surgical complete blood counts performed over 2 days on a UniCel DxH 800 analyzer (Beckman Coulter, USA) using samples collected in vacutainer tubes containing di-Potassium ethylene diamine tetra acetate (EDTA) anticoagulant showed variable platelet counts ranging from 9000/cu mm to 39,000/cu mm with the normal hemoglobin and high normal or mildly elevated white cell counts. Peripheral blood smear examination of all the samples showed large platelet aggregates suggesting PTP. [Figure 1] shows the histograms obtained on the automated analyser and [Figure 2] shows platelet aggregates observed on the smear. Manual platelet counts were invalid as the counting chamber showed large platelet aggregates. A sample collected in 3.8% sodium citrate too showed PTP with a platelet count of 30,000/cu mm on the analyzer. Subsequently one of the samples, which was collected in EDTA and showed a count of 29,000/cu mm was incubated at 37°C for 20 min and reanalyzed. The platelet count on the analyzer increased to 76,000/cu mm. To this incubated sample, 20 mg Kanamycin was added. Following this intervention, the platelet count on the analyzer increased to 89,000/cu mm. Further incubation until 40 min showed a count of 96,000/cu mm [Table 1].
Figure 1: Histograms obtained with platelet aggregates (on the left ) and a normal sample for contrast (on the right). Note that in the former, the platelet histogram is skewed to the right and the white blood cells histogram shows evidence of interference (encircled)

Click here to view
Figure 2: Platelet aggregates observed on the smear

Click here to view
Table 1: Complete blood counts obtained on initial sample and sample treated with Kanamycin

Click here to view


Meanwhile, in view of the ambiguous platelet count in this critical scenario, 6 units of platelet concentrate had been transfused. On the basis of the final platelet count following addition of Kanamycin, it was decided that further prophylactic peri-operative platelet transfusion support was not indicated. The patient underwent surgery the following day and recuperated uneventfully.


   Discussion Top


EDTA induced PTP was first reported by Gowland et al.[1] (1969). It is attributed to EDTA induced alteration of surface glycoproteins (GP) and anionic phospholipids, which enables binding of antiplatelet antibodies, which in turn cause agglutination. Antibodies against the platelet GPIIb/IIIa have been reported in this context. [2] Platelet agglutinins generally belong to the immunoglobulin M class. However, immunoglobulin G and immunoglobulin A are also described. [3] Around 20% of cases with EDTA induced PTP show the phenomenon in citrate anticoagulant as well. [3],[4] Oxalate and heparin have also been implicated in PTP. One study suggested that PTP seen non-specifically among calcium chelators was caused by deprivation of calcium from the cell membrane, causing conformational changes that produced neoantigens and subsequent antibody mediated agglutination. However, PTP caused by EDTA alone appeared to be independent of calcium levels. [4] Normal platelet function seems to be a criterion for platelet aggregation. [5]

Most aggregating antibodies are cold reacting and are inhibited by incubation at 37°C, though PTP reportedly persists even at 37°C in 20% of cases. [3] Sakurai et al.[6] reported the inhibition of PTP by Kanamycin when pre-supplemented with EDTA as well as dissociation of platelet aggregates when Kanamycin was added within 30 min following blood collection. Though the mechanism of this action was unclear, morphology, complete blood counts and histograms were not significantly altered by this drug. In the light of this finding, we chose to use Kanamycin in addition to warm incubation to aid in the resolution of the spurious platelet count in our patient.

PTP has been found more frequently in patients on medication as well as severely ill patients, in association with autoimmune, neoplastic, atherosclerosis related and liver related conditions. [7] The incidence has been reported to be 0.013% in blood donors, 0.11-0.15% among out-patients and 1.9% among hospitalized patients. [8],[9],[10]

One author reported finding a normal platelet and leukocyte histogram in 10% of cases of PTP, which questions the sensitivity of the histogram in the detection of these cases. [8] Review of the peripheral smear and platelet histogram as well as a carefully taken clinical history are imperative where the platelet count is a matter of clinical concern and particularly before any intervention for thrombocytopenia is considered.

 
   References Top

1.Gowland E, Kay HE, Spillman JC, Williamson JR. Agglutination of platelets by a serum factor in the presence of EDTA. J Clin Pathol 1969;22:460-4.  Back to cited text no. 1
    
2.Wilkes NJ, Smith NA, Mallett SV. Anticoagulant-induced pseudothrombocytopenia in a patient presenting for coronary artery bypass grafting. Br J Anaesth 2000;84:640-2.  Back to cited text no. 2
    
3.Bizzaro N. EDTA-dependent pseudothrombocytopenia: A clinical and epidemiological study of 112 cases, with 10-year follow-up. Am J Hematol 1995;50:103-9.  Back to cited text no. 3
    
4.Onder O, Weinstein A, Hoyer LW. Pseudothrombocytopenia caused by platelet agglutinins that are reactive in blood anticoagulated with chelating agents. Blood 1980;56:177-82.  Back to cited text no. 4
    
5.Akbayram S, Dogan M, Akgun C, Caksen H, Oner AF. EDTA-dependent pseudothrombocytopenia in a child. Clin Appl Thromb Hemost 2011;17:494-6.  Back to cited text no. 5
    
6.Sakurai S, Shiojima I, Tanigawa T, Nakahara K. Aminoglycosides prevent and dissociate the aggregation of platelets in patients with EDTA-dependent pseudothrombocytopenia. Br J Haematol 1997;99:817-23.  Back to cited text no. 6
    
7.Berkman N, Michaeli Y, Or R, Eldor A. EDTA-dependent pseudothrombocytopenia: A clinical study of 18 patients and a review of the literature. Am J Hematol 1991;36:195-201.  Back to cited text no. 7
    
8.García Suárez J, Merino JL, Rodríguez M, Velasco A, Moreno MC. Pseudothrombocytopenia: Incidence, causes and methods of detection. Sangre (Barc) 1991;36:197-200.  Back to cited text no. 8
    
9.Maslanka K, Marciniak-Bielak D, Szczepinski A. Pseudothrombocytopenia in blood donors. Vox Sang 2008;95:349.  Back to cited text no. 9
    
10.Froom P, Barak M. Prevalence and course of pseudothrombocytopenia in outpatients. Clin Chem Lab Med 2011;49:111-4.  Back to cited text no. 10
    

Top
Correspondence Address:
Mary Purna Chacko
Department of Transfusion Medicine and Immunohaematology, Christian Medical College and Hospital, Vellore - 632 004, Tamil Nadu
India
Login to access the Email id

Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0377-4929.120407

Rights and Permissions


    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

  [Table 1]



 

Top
 
 
  Search
 
    Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
    Email Alert *
    Add to My List *
* Registration required (free)  


    Abstract
   Introduction
   Case Report
   Discussion
    References
    Article Figures
    Article Tables

 Article Access Statistics
    Viewed4110    
    Printed102    
    Emailed1    
    PDF Downloaded155    
    Comments [Add]    

Recommend this journal