Asian Journal of Transfusion Science
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LETTER TO THE EDITOR Table of Contents   
Year : 2013  |  Volume : 7  |  Issue : 1  |  Page : 92-93
Rapid diagnosis of heparin-induced thrombocytopenia using a particle gel immunoassay in at-risk cardiac surgery patients


1 Department of Transfusion Medicine, Global Health City, Chennai, India
2 Department of Cardio Vascular and Thoracic Surgery, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India
3 Department of Transfusion Medicine, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India

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Date of Web Publication2-Feb-2013
 

How to cite this article:
Sachan D, Gupta N, Chaudhary R. Rapid diagnosis of heparin-induced thrombocytopenia using a particle gel immunoassay in at-risk cardiac surgery patients. Asian J Transfus Sci 2013;7:92-3

How to cite this URL:
Sachan D, Gupta N, Chaudhary R. Rapid diagnosis of heparin-induced thrombocytopenia using a particle gel immunoassay in at-risk cardiac surgery patients. Asian J Transfus Sci [serial online] 2013 [cited 2021 Oct 23];7:92-3. Available from: https://www.ajts.org/text.asp?2013/7/1/92/106765


Sir,

Heparin-induced thrombocytopenia (HIT) is a condition characterized by a thrombocytopenia or thrombosis with a temporal relationship of 1-2 weeks after the initiation of heparin. [1] Although the diagnosis of HIT may be suspected on clinical grounds alone, the decision to discontinue heparin in a patient with a recent thrombotic event often poses a therapeutic dilemma especially when other potential causes of thrombocytopenia may be present. Therefore, laboratory conformation of the diagnosis is often desirable. Several assays such as serotonin release assay (SRA), heparin-induced platelet aggregation (HIPA), flow cytometry, and H-PF4 enzyme-linked immunosorbent assay (ELISA) have been developed to affirm or to exclude the diagnosis of HIT. [1] Each method has its own advantages and disadvantages. The tests HIPA and SRA are highly specific, but they are laborious and require selected donor platelets and extended experience. High titre immunoglobulin (IgG) antibodies correlate with clinical HIT, but ELISA is also time-consuming.

The particle gel immunoassay (PaGIA) (ID-PaGIA H/PF4, DiaMed, Cressiers/Morat, Switzerland) is a rapid assay for detection of anti-PF4/heparin antibodies. This assay uses PF4/heparin complexes bound to red, high-density polystyrene beads; after addition of patient serum or plasma, the anti-PF4/heparin antibodies bind to the antigen-coated beads. This assay has been adapted to the gel technique of the ID microtyping. This method is available to blood banks that use a gel centrifugation technology system. We evaluated PaGIA for the rapid diagnosis of HIT in patients undergoing cardiac surgery at our hospital.

The study was conducted in the Department of Transfusion Medicine in collaboration with Department of Cardio Vascular and Thoracic Surgery at our tertiary care institute. A total of 100 adult male and non-pregnant female patients undergoing open heart cardiac surgery (valvular replacement surgery/coronary artery bypass graft/combined) were monitored for baseline, and postoperative platelet counts from day 1 to day 14. Definite thrombocytopenia was defined as more than 50% fall in the platelet count from the baseline or counts <100 × 10 5 /μl. Clinical T scoring was done according to Warkentin. [2] All the patients were further investigated for H-PF4 antibody using PaGIA and ELISA. Patients with clinical thrombocytopenia with the presence of H-PF4 antibody with high/intermediate T score were considered to be clinical HIT.

PaGIA was performed on serum of 42 patients with definite thrombocytopenia at the baseline level and at day 7. Out of 42 patients, 10 patients had positive results at day 7 and all were negative at the baseline level. There was a good concordance between PaGIA and ELISA for detection of HPF4 antibodies. Out of 19 ELISA positive patients, 10 were also PaGIA positive, while all the ELISA negative patient samples were also PaGIA negative. There was a good correlation of PaGIA-positive results with a high T score. Of the eight patients with high scores, six were PaGIA positive. All these six patients were also ELISA positive.

In the last decade, gel technology has replaced the conventional test tube method for various immunohematological procedures. It is also being used for the lab diagnosis of paroxysmal nocturnal hemoglobinuria, fetomaternal hemorrhage, and serological diagnosis of syphilis. We report here the use of this technology for rapid diagnosis of HIT in blood bank settings.

Our results are in agreement with other studies, in which PaGIA is compared with SRA and HIPA and showed comparable results. [3] However, it was recommended that this assay should be used in combination with a functional assay using washed platelets in order also to detect HIT antibodies against other antigens involved in HIT, such as IL-8 or neutrophil activating peptides. Alberio et al. [4] demonstrated that titration of H-PF4 antibodies using PaGIA permits better recognition of clinically relevant antibody levels than those using a qualitative test without titration. Of their 69 patients with H-PF4 antibodies, HIT was "very likely" when the tier was >4. The performance of PaGIA with clinical T scores in clinically suspected HIT patients was similar to other studies. [5]

In our experience, PaGIA is rapid and easy to perform. It allows macroscopic evaluation of test results after a few minutes. It does not require advanced training and can be easily adapted in blood bank settings. In addition to a series of samples, individual patient samples can also be investigated effectively. Moreover, unlike SRA or HIPA it does not require freshly prepared platelets. Thus, PaGIA is a reliable tool for detection of HIT antibodies in blood bank settings as most of the advanced blood centers are already using in ID micro typing system for blood grouping and cross matching.

The high mortality associated with HIT led to an increasing demand for its laboratory exclusion in patients with various clinical conditions that mimic HIT, particularly because multimorbid patients are more likely to form PF4 antibodies. The clinical score is highly reliable to exclude HIT when clinical features are unambiguous, but a rapid assay is desirable for patients with undeterminable probability for HIT. Commercial ELISA besides confirming the diagnosis gives additional information such as prediction of thrombosis.

Rapid assays which are easy to implement in blood bank settings are now being introduced. In our experience, PaGIA is a good supplement for ELISA as a screening test in clinically suspected patients. It can also be used as a baseline test before administration of heparin.

 
   References Top

1.Warkentin TE, Greinacher A. Laboratory testing for heparin-induced thrombocytopenia. In: Warkentin TE, Greinacher A, editors. Heparin-Induced Thrombocytopenia. 3rd ed. New York, NY: Marcel Dekker; 2004. p. 271-311.  Back to cited text no. 1
    
2.Warkentin TE. Heparin-induced thrombocytopenia: Pathogenesis and management. Br J Haematol 2003;121:535-55.  Back to cited text no. 2
[PUBMED]    
3.Eichler P, Raschke R, Lubenow N, Meyer O, Schwind P, Greinacher A. The new ID-heparin/PF4 antibody test for rapid detection of heparin-induced antibodies in comparison with functional and antigenic assays. Br J Haematol 2002;116:887-91.  Back to cited text no. 3
[PUBMED]    
4.Alberio L, Kimmerle S, Baumann A, Taleghani BM, Biasiutti FD, Lammle B. Rapid determination of anti-heparin/platelet factor 4 antibody titers in the diagnosis of Heparin- induced thrombocytopenia. Am J Med 2003;114:528-36.  Back to cited text no. 4
    
5.Pouplard C, Gueret P, Fouassier M, Ternisien C, Trossaert M, Re'gina S, et al. Prospective evaluation of the 4Ts score and particle gel immunoassay specific to heparin/PF4 for the diagnosis of heparin-induced thrombocytopenia. J Thromb Haemost 2007;5:1373-9.  Back to cited text no. 5
    

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Correspondence Address:
Deepti Sachan
Department of Transfusion Medicine, Global Health City, Chennai 600 100
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0973-6247.106765

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2006 - Asian Journal of Transfusion Science | Published by Wolters Kluwer - Medknow
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