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Zlamal J, Aliotta A, Alberio L, Chen V, Bakchoul T. Diagnostic value of antibody-induced procoagulant platelets in heparin-induced thrombocytopenia: communication from the ISTH SSC Subcommittee on Platelet Immunology. J Thromb Haemost 2024; 22:860-868. [PMID: 38065529 DOI: 10.1016/j.jtha.2023.11.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Revised: 11/20/2023] [Accepted: 11/21/2023] [Indexed: 12/30/2023]
Abstract
Heparin-induced thrombocytopenia (HIT) is an immune-mediated prothrombotic disorder characterized by a drop in platelet count and an increased risk of thromboembolic events. The accurate diagnosis of HIT involves clinical assessment and laboratory testing with well-characterized functional tests. Recent research has shown the potential of investigating procoagulant platelet formation induced by HIT antibodies. To successfully implement these assays in clinical laboratories, careful consideration of technical and preanalytical factors is crucial. In this communication from the SSC Platelet Immunology, we provide a consensus from experts on the use of flow cytometry in HIT diagnosis, highlighting the importance of standardized protocols.
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Affiliation(s)
- Jan Zlamal
- Institute for Clinical and Experimental Transfusion Medicine, Medical Faculty of Tübingen, University of Tübingen, Tübingen, Germany; Centre for Clinical Transfusion Medicine, Tübingen, Germany
| | - Alessandro Aliotta
- Division of Hematology and Central Hematology Laboratory, Lausanne University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland
| | - Lorenzo Alberio
- Division of Hematology and Central Hematology Laboratory, Lausanne University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland
| | - Vivien Chen
- ANZAC Research Institute, Sydney Local Health District, Sydney, New South Wales, Australia; Department of Haematology, Concord Repatriation General Hospital and NSW Health Pathology, Sydney, New South Wales, Australia; Concord Clinical School, University of Sydney, Sydney, New South Wales, Australia
| | - Tamam Bakchoul
- Institute for Clinical and Experimental Transfusion Medicine, Medical Faculty of Tübingen, University of Tübingen, Tübingen, Germany; Centre for Clinical Transfusion Medicine, Tübingen, Germany.
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Tardy-Poncet B, de Maistre E, Pouplard C, Presles E, Alhenc-Gelas M, Lasne D, Horellou MH, Mouton C, Serre-Sapin A, Bauters A, Nguyen P, Mullier F, Perrin J, Le Gal G, Morange PE, Grunebaum L, Lillo-Le Louet A, Elalamy I, Gruel Y, Greinacher A, Lecompte T, Tardy B. Heparin-induced thrombocytopenia: Construction of a pretest diagnostic score derived from the analysis of a prospective multinational database, with internal validation. J Thromb Haemost 2021; 19:1959-1972. [PMID: 33872452 DOI: 10.1111/jth.15344] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 04/09/2021] [Accepted: 04/09/2021] [Indexed: 12/18/2022]
Abstract
BACKGROUND Diagnosis of heparin-induced thrombocytopenia (HIT) requires pretest probability assessment and dedicated laboratory assays. OBJECTIVE To develop a pretest score for HIT. DESIGN Observational; analysis of prospectively collected data of hospitalized patients suspected with HIT (ClinicalTrials.gov NCT00748839). SETTING Thirty-one tertiary hospitals in France, Switzerland, and Belgium. PATIENTS Patients tested for HIT antibodies (2280 evaluable), randomly allocated to derivation and validation cohorts. MEASUREMENTS Independent adjudicators diagnosed HIT based on the prospectively collected data and serotonin release assay results. RESULTS Heparin-induced thrombocytopenia was diagnosed in 234 (14.7%) and 99 (14.5%) patients in the two cohorts. Eight features were associated with HIT (in brackets, points assigned for score calculation of the score): unfractionated heparin (1); therapeutic-dose heparin (1); cardiopulmonary bypass (cardiac surgery) (2); major trauma (3); 5- to 21-day interval from anticoagulation initiation to suspicion of HIT (4); ≥40% decrease in platelet count over ≤6 days (3); thrombotic event, arterial (3) or venous (3). The C-statistic was 0.79 (95% CI, 0.76-0.82). In the validation cohort, the area under the receiver operating characteristic curve was 0.77 (95% CI, 0.74-0.80). Three groups of scores were defined; HIT prevalence reached almost 30% in the high-probability group. LIMITATION The performance of the score may depend on settings and practices. CONCLUSION The objective, easy-to-collect, clinical features of HIT we evidenced were incorporated into a pretest score, which may guide clinical decisions regarding diagnostic testing and anticoagulation.
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Affiliation(s)
- Brigitte Tardy-Poncet
- CIC 1408, Inserm U1059 SAINBIOSE, F-Crin INNOVTE, Université de Lyon, Saint-Etienne, France
| | | | - Claire Pouplard
- Division of Hematology - Hemostasis, University Hospital of Tours, Tours, France
| | - Emilie Presles
- CIC 1408, Inserm U1059 SAINBIOSE, F-Crin INNOVTE, Université de Lyon, Saint-Etienne, France
| | | | - Dominique Lasne
- Hemostasis Unit, Hôpital Necker, AP-HP, Paris, France
- Université Paris Sud Paris Saclay, Inserm U1176, Le Kremlin-Bicêtre, France
| | | | | | | | | | | | - François Mullier
- Namur Thrombosis and Hemostasis Center, Hematology Laboratory, Université catholique de Louvain, CHU UCL Namur, Yvoir, Belgium
| | | | - Grégoire Le Gal
- Department of Medicine, University of Ottawa, Ottawa Hospital Research Institute, Thrombosis Research Group, Ottawa, ON, Canada
| | - Pierre-Emmanuel Morange
- C2VN, Aix Marseille University, INSERM, INRA; Laboratory of Hematology, La Timone Hospital, Assistance Publique des Hôpitaux de Marseille, Marseille, France
| | - Lélia Grunebaum
- Laboratory of Hematology, CHU Strasbourg, Strasbourg, France
| | - Agnès Lillo-Le Louet
- Pharmacovigilance Center, Georges Pompidou European Hospital, AP-HP, Paris, France
| | - Ismail Elalamy
- Hematology and Thrombosis Center, Tenon University Hospital, INSERM UMRS 938, Sorbonne University, Paris, France
| | - Yves Gruel
- Division of Hematology - Hemostasis, University Hospital of Tours, Tours, France
| | - Andreas Greinacher
- Institut fuer Immunologie und Transfusionsmedizin, Universitaetsmedizin Greifswald, Greifswald, Germany
| | - Thomas Lecompte
- Department of Medicine, Geneva University Hospitals, and Geneva Platelet Group (GpG), Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Bernard Tardy
- CIC 1408, Inserm U1059 SAINBIOSE, F-Crin INNOVTE, Université de Lyon, Saint-Etienne, France
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An Optimized and Standardized Rapid Flow Cytometry Functional Method for Heparin-Induced Thrombocytopenia. Biomedicines 2021; 9:biomedicines9030296. [PMID: 33805718 PMCID: PMC7999851 DOI: 10.3390/biomedicines9030296] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Revised: 03/04/2021] [Accepted: 03/10/2021] [Indexed: 11/17/2022] Open
Abstract
Heparin-induced thrombocytopenia (HIT) is a thrombocytopenia caused by heparin and mediated by an atypical immune mechanism leading to a paradoxical high thrombotic risk, associated with severe morbidity or death. The diagnosis of HIT combines a clinical scoring of pretest probability and laboratory testing. First-line routine tests are antigen binding assays detecting specific antibodies. The most sensitive of these tests have a high HIT-negative predictive value enabling HIT diagnosis to be ruled out when negative. However, HIT-positive predictive value is low, and a functional assay evaluating the pathogenicity of the antibodies should be performed to exclude false-positive results. In contrast to screening assays, functional assays are highly specific but technically challenging, and are thus performed in referral laboratories, where platelet activation is detected using radioactive serotonin (serotonin release assay, SRA) or visually (heparin-induced platelet activation, HIPA). Flow cytometry is a possible alternative. It is, however, currently not widely used, mostly because of the lack of standardization of the published assays. This article describes and discusses the standardization of a HIT flow cytometry assay (HIT-FCA) method, which subsequently led to the development and commercialization of a CE-marked assay (HIT Confirm®, Emosis, France) as a suitable rapid HIT functional test.
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Warkentin TE, Smythe MA, Ali MA, Aslam N, Sheppard JI, Smith JW, Moore JC, Arnold DM, Nazy I. Serotonin-release assay-positive but platelet factor 4-dependent enzyme-immunoassay negative: HIT or not HIT? Am J Hematol 2021; 96:320-329. [PMID: 33326124 DOI: 10.1002/ajh.26075] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 12/07/2020] [Accepted: 12/14/2020] [Indexed: 12/28/2022]
Abstract
IgG-specific and polyspecific PF4-dependent enzyme-immunoassays (EIAs) have exceptionally high sensitivity (≥99%) for diagnosis of heparin-induced thrombocytopenia (HIT), a drug reaction caused by platelet-activating antibodies detectable by serotonin-release assay (SRA). The IgG-specific EIAs are recommended for screening, as their high sensitivity is accompanied by relatively high specificity vis-à-vis polyspecific EIAs. We investigated the frequency of SRA-positive/EIA-negative (SRA+/EIA-) HIT, prompted by referral to our reference HIT laboratory of serial blood samples from a patient ("index case") with false-negative IgG-specific EIAs. Despite initial clinical suspicion for HIT, repeat negative IgG-specific EIAs prompted heparin resumption, which triggered recurrent thrombocytopenia and near-fatal cardiac arrest, indicating likely post-heparin HIT-associated anaphylactoid reaction. Further investigations revealed a strong-positive SRA, whether performed with heparin alone, PF4 alone, or PF4/heparin, with inhibition by Fc receptor-blocking monoclonal antibody (indicating IgG-mediated platelet activation); however, five different IgG-specific immunoassays yielded primarily negative (or weak-positive) results. To investigate the frequency of SRA+/EIA- HIT, we reviewed the laboratory and clinical features of patients with this serological profile during a 6-year period in which our reference laboratory investigated for HIT using both SRA and IgG-specific EIA. Although ~0.2% of 8546 patients had an SRA+/EIA- profile, further review of 15 such cases indicated clerical/laboratory misclassification or false-positive SRA in all, with no SRA+/EIA- HIT case identified. We conclude that while SRA+/EIA- HIT is possible-as shown by our index case-this clinical picture is exceptionally uncommon. Moreover, the requirement for a positive EIA is a useful quality control maneuver that reduces risk of reporting a false-positive SRA result.
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Affiliation(s)
- Theodore E. Warkentin
- Department of Pathology and Molecular Medicine Michael G. DeGroote School of Medicine Hamilton Ontario Canada
- Department of Medicine Michael G. DeGroote School of Medicine Hamilton Ontario Canada
- McMaster Centre for Transfusion Research Hamilton Ontario Canada
| | - Maureen A. Smythe
- Department of Pharmaceutical Services Beaumont Hospital Royal Oak Michigan USA
- Department of Pharmacy Practice Wayne State University Detroit Michigan USA
- Oakland University William Beaumont School of Medicine Rochester Michigan USA
| | - Mona A. Ali
- Department of Pharmaceutical Services Beaumont Hospital Royal Oak Michigan USA
| | - Naveed Aslam
- Oakland University William Beaumont School of Medicine Rochester Michigan USA
| | - Jo‐Ann I. Sheppard
- Department of Pathology and Molecular Medicine Michael G. DeGroote School of Medicine Hamilton Ontario Canada
| | - James W. Smith
- Department of Medicine Michael G. DeGroote School of Medicine Hamilton Ontario Canada
| | - Jane C. Moore
- Department of Medicine Michael G. DeGroote School of Medicine Hamilton Ontario Canada
| | - Donald M. Arnold
- Department of Medicine Michael G. DeGroote School of Medicine Hamilton Ontario Canada
- McMaster Centre for Transfusion Research Hamilton Ontario Canada
| | - Ishac Nazy
- Department of Medicine Michael G. DeGroote School of Medicine Hamilton Ontario Canada
- McMaster Centre for Transfusion Research Hamilton Ontario Canada
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Evaluation of a flow cytometer-based functional assay using platelet-rich plasma in the diagnosis of heparin-induced thrombocytopenia. Thromb Res 2019; 180:55-61. [PMID: 31220752 DOI: 10.1016/j.thromres.2019.05.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Revised: 05/07/2019] [Accepted: 05/20/2019] [Indexed: 01/25/2023]
Abstract
BACKGROUND Heparin-induced thrombocytopenia (HIT) is caused by platelet-activating antibodies that recognize platelet factor 4/heparin (PF4/hep)-complexes. The in vitro demonstration of PF4/hep antibodies using functional assays is essential for an optimal management of patients suspected to have HIT. However, conventional functional assays are technically challenging and limited to specialized laboratories. In contrast, flow cytometers are commonly used in routine laboratories. The aim of this study is to investigate the performance characteristics of a commercially available, flow cytometer based assay in the diagnosis of HIT. STUDY DESIGN Sera of consecutive patients with suspected HIT were investigated using the Emo-test HIT Confirm® assay and compared to the standard method consisting of an IgG-specific enzyme immunoassay (EIA) for anti-PF4/hep antibodies and the heparin induced platelet aggregation (HIPA) test. RESULTS 390 sera were included in the study, 164 sera tested IgG EIA-positive, of which 33 also tested HIPA-positive. No HIPA-positive samples were EIA-negative. In the Emo-test HIT Confirm® assay, 112 sera revealed positive results (%Hepla > 13); however, 51 (45.5%) were EIA-negative. Of the 33 HIPA-positive/EIA-positive HIT sera, 23 tested positive in the Emo-test HIT Confirm® assay, 2 gave ambiguous results, and 8 sera yielded false-negative results. Accordingly, the HIT Confirm® assay showed a sensitivity of 69.7% with a slightly better specificity of 75.4% compared to the EIA (sensitivity 100%, specificity 63.3%). An increase in diagnostic specificity for HIT to 85% was found when positive results were obtained in both the Emo-test HIT Confirm® assay and EIA. CONCLUSION The Emo-Test HIT Confirm® assay may improve the specificity of laboratory investigations of HIT. However, the assay can only be recommended in combination with an immunoassay due to the high rate of false negativity. Our observation indicates a need to establish external quality assessment for functional assays to avoid such clinically relevant pitfalls.
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Heparin-Induced Thrombocytopenia. Platelets 2019. [DOI: 10.1016/b978-0-12-813456-6.00041-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Raschke RA, Gallo T, Curry SC, Whiting T, Padilla-Jones A, Warkentin TE, Puri A. Clinical effectiveness of a Bayesian algorithm for the diagnosis and management of heparin-induced thrombocytopenia. J Thromb Haemost 2017; 15:1640-1645. [PMID: 28622439 DOI: 10.1111/jth.13758] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Indexed: 11/28/2022]
Abstract
Essentials We previously published a diagnostic algorithm for heparin-induced thrombocytopenia (HIT). In this study, we validated the algorithm in an independent large healthcare system. The accuracy was 98%, sensitivity 82% and specificity 99%. The algorithm has potential to improve accuracy and efficiency in the diagnosis of HIT. SUMMARY Background Heparin-induced thrombocytopenia (HIT) is a life-threatening drug reaction caused by antiplatelet factor 4/heparin (anti-PF4/H) antibodies. Commercial tests to detect these antibodies have suboptimal operating characteristics. We previously developed a diagnostic algorithm for HIT that incorporated 'four Ts' (4Ts) scoring and a stratified interpretation of an anti-PF4/H enzyme-linked immunosorbent assay (ELISA) and yielded a discriminant accuracy of 0.97 (95% confidence interval [CI], 0.93-1.00). Objectives The purpose of this study was to validate the algorithm in an independent patient population and quantitate effects that algorithm adherence could have on clinical care. Methods A retrospective cohort comprised patients who had undergone anti-PF4/H ELISA and serotonin release assay (SRA) testing in our healthcare system from 2010 to 2014. We determined the algorithm recommendation for each patient, compared recommendations with the clinical care received, and enumerated consequences of discrepancies. Operating characteristics were calculated for algorithm recommendations using SRA as the reference standard. Results Analysis was performed on 181 patients, 10 of whom were ruled in for HIT. The algorithm accurately stratified 98% of patients (95% CI, 95-99%), ruling out HIT in 158, ruling in HIT in 10 and recommending an SRA in 13 patients. Algorithm adherence would have obviated 165 SRAs and prevented 30 courses of unnecessary antithrombotic therapy for HIT. Diagnostic sensitivity was 0.82 (95% CI, 0.48-0.98), specificity 0.99 (95% CI, 0.97-1.00), PPV 0.90 (95% CI, 0.56-0.99) and NPV 0.99 (95% CI, 0.96-1.00). Conclusions An algorithm incorporating 4Ts scoring and a stratified interpretation of the anti-PF4/H ELISA has good operating characteristics and the potential to improve management of suspected HIT patients.
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Affiliation(s)
- R A Raschke
- Division of Clinical Data Analytics and Decision Support, Department of Medicine, University of Arizona College of Medicine - Phoenix, Phoenix, AZ, USA
- Department of Critical Care Medicine, Banner - University Medical Center Phoenix, Phoenix, AZ, USA
| | - T Gallo
- Division of Clinical Data Analytics and Decision Support, Department of Medicine, University of Arizona College of Medicine - Phoenix, Phoenix, AZ, USA
| | - S C Curry
- Division of Clinical Data Analytics and Decision Support, Department of Medicine, University of Arizona College of Medicine - Phoenix, Phoenix, AZ, USA
- Department of Medical Toxicology, Banner - University Medical Center Phoenix, Phoenix, AZ, USA
| | - T Whiting
- Department of Critical Care Medicine, Banner - University Medical Center Phoenix, Phoenix, AZ, USA
| | - A Padilla-Jones
- Banner Research Institute, Banner - University Medical Center Phoenix, Phoenix, AZ, USA
| | - T E Warkentin
- Department of Pathology and Molecular Medicine, and Department of Medicine, Michael G. DeGroote School of Medicine, McMaster University, Hamilton, ON, Canada
| | - A Puri
- Internal Medicine Residency, University of Arizona College of Medicine Phoenix, Phoenix, AZ, USA
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Minet V, Dogné JM, Mullier F. Functional Assays in the Diagnosis of Heparin-Induced Thrombocytopenia: A Review. Molecules 2017; 22:molecules22040617. [PMID: 28398258 PMCID: PMC6153750 DOI: 10.3390/molecules22040617] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Revised: 04/05/2017] [Accepted: 04/08/2017] [Indexed: 01/09/2023] Open
Abstract
A rapid and accurate diagnosis in patients with suspected heparin-induced thrombocytopenia (HIT) is essential for patient management but remains challenging. Current HIT diagnosis ideally relies on a combination of clinical information, immunoassay and functional assay results. Platelet activation assays or functional assays detect HIT antibodies that are more clinically significant. Several functional assays have been developed and evaluated in the literature. They differ in the activation endpoint studied; the technique or technology used; the platelet donor selection; the platelet suspension (washed platelets, platelet rich plasma or whole blood); the patient sample (serum or plasma); and the heparin used (type and concentrations). Inconsistencies in controls performed and associated results interpretation are common. Thresholds and performances are determined differently among papers. Functional assays suffer from interlaboratory variability. This lack of standardization limits the evaluation and the accessibility of functional assays in laboratories. In the present article, we review all the current activation endpoints, techniques and methodologies of functional assays developed for HIT diagnosis.
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Affiliation(s)
- Valentine Minet
- Department of Pharmacy, Namur Thrombosis and Hemostasis Center (NTHC), Namur Research Institute for LIfe Sciences (NARILIS), University of Namur, Namur 5000, Belgium.
| | - Jean-Michel Dogné
- Department of Pharmacy, Namur Thrombosis and Hemostasis Center (NTHC), Namur Research Institute for LIfe Sciences (NARILIS), University of Namur, Namur 5000, Belgium.
| | - François Mullier
- CHU UCL Namur, Namur Thrombosis and Hemostasis Center (NTHC), Hematology Laboratory, Université catholique de Louvain, Yvoir 5530, Belgium.
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Sono-Koree NK, Crist RA, Frank EL, Rodgers GM, Smock KJ. A high-performance liquid chromatography method for the serotonin release assay is equivalent to the radioactive method. Int J Lab Hematol 2015; 38:72-80. [DOI: 10.1111/ijlh.12442] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Accepted: 09/16/2015] [Indexed: 11/28/2022]
Affiliation(s)
- N. K. Sono-Koree
- ARUP Laboratories Institute for Clinical and Experimental Pathology; Salt Lake City UT USA
| | - R. A. Crist
- ARUP Laboratories Institute for Clinical and Experimental Pathology; Salt Lake City UT USA
| | - E. L. Frank
- ARUP Laboratories Institute for Clinical and Experimental Pathology; Salt Lake City UT USA
- Department of Pathology; University of Utah Health Sciences Center; Salt Lake City UT USA
| | - G. M. Rodgers
- ARUP Laboratories Institute for Clinical and Experimental Pathology; Salt Lake City UT USA
- Department of Pathology; University of Utah Health Sciences Center; Salt Lake City UT USA
- Department of Internal Medicine; University of Utah Health Sciences Center; Salt Lake City UT USA
| | - K. J. Smock
- ARUP Laboratories Institute for Clinical and Experimental Pathology; Salt Lake City UT USA
- Department of Pathology; University of Utah Health Sciences Center; Salt Lake City UT USA
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Weintraub L, Driscoll C, Aydin S, Lamour JM, Weinstein S, Manwani D. Challenging diagnosis and treatment of HIT in child with ventricular assistance device. Pediatr Transplant 2015; 19:E152-6. [PMID: 26087151 DOI: 10.1111/petr.12540] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 05/20/2015] [Indexed: 11/28/2022]
Abstract
HIT presents the clinician with unique diagnostic challenges, especially in the pediatric population. The HIT clinical sequelae of thrombocytopenia and thrombosis are secondary to the activation of platelets by heparin-antibody complexes. Diagnosis involves clinical observations and confirmatory laboratory testing using antibody detection and the functional SRA. As we describe in the following case of a six-yr-old female, the SRA may be difficult to interpret in the case of high-titer antibodies and illustrates the need for repeat testing in cases of high clinical suspicion.
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Affiliation(s)
- Lauren Weintraub
- Division of Hematology/Oncology, Department of Pediatrics, Children's Hospital at Montefiore, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Catherine Driscoll
- Division of Hematology/Oncology, Department of Pediatrics, Children's Hospital at Montefiore, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Scott Aydin
- Division of Cardiology, Department of Pediatrics, Children's Hospital at Montefiore, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Jaqueline M Lamour
- Division of Cardiology, Department of Pediatrics, Children's Hospital at Montefiore, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Sam Weinstein
- Department of Cardiovascular and Thoracic Surgery, Children's Hospital at Montefiore, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Deepa Manwani
- Division of Hematology/Oncology, Department of Pediatrics, Children's Hospital at Montefiore, Albert Einstein College of Medicine, Bronx, NY, USA
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Warkentin TE, Arnold DM, Nazi I, Kelton JG. The platelet serotonin-release assay. Am J Hematol 2015; 90:564-72. [PMID: 25775976 DOI: 10.1002/ajh.24006] [Citation(s) in RCA: 111] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Revised: 03/05/2015] [Accepted: 03/08/2015] [Indexed: 12/24/2022]
Abstract
Few laboratory tests are as clinically useful as The platelet serotonin-release assay (SRA): a positive SRA in the appropriate clinical context is virtually diagnostic of heparin-induced thrombocytopenia (HIT), a life- and limb-threatening prothrombotic disorder caused by anti-platelet factor 4 (PF4)/heparin antibodies that activate platelets, thereby triggering serotonin-release. The SRA's performance characteristics include high sensitivity and specificity, although caveats include indeterminate reaction profiles (observed in ∼4% of test sera) and potential for false-positive reactions. As only a subset of anti-PF4/heparin antibodies detectable by enzyme-immunoassay (EIA) are additionally platelet-activating, the SRA has far greater diagnostic specificity than the EIA. However, requiring a positive EIA, either as an initial screening test or as an SRA adjunct, will reduce risk of a false-positive SRA (since a negative EIA in a patient with a "positive" SRA should prompt critical evaluation of the SRA reaction profile). The SRA also provides useful information on whether a HIT serum produces strong platelet activation even in the absence of heparin: such heparin-"independent" platelet activation is a marker of unusually severe HIT, including delayed-onset HIT and severe HIT complicated by consumptive coagulopathy with risk for microvascular thrombosis.
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Affiliation(s)
- Theodore E. Warkentin
- Department of Pathology and Molecular Medicine; Michael G. DeGroote School of Medicine; McMaster University; Hamilton Ontario Canada
- Department of Medicine; Michael G. DeGroote School of Medicine; McMaster University; Hamilton Ontario Canada
| | - Donald M. Arnold
- Department of Medicine; Michael G. DeGroote School of Medicine; McMaster University; Hamilton Ontario Canada
| | - Ishac Nazi
- Department of Medicine; Michael G. DeGroote School of Medicine; McMaster University; Hamilton Ontario Canada
| | - John G. Kelton
- Department of Pathology and Molecular Medicine; Michael G. DeGroote School of Medicine; McMaster University; Hamilton Ontario Canada
- Department of Medicine; Michael G. DeGroote School of Medicine; McMaster University; Hamilton Ontario Canada
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12
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Nazi I, Arnold DM, Smith JW, Horsewood P, Moore JC, Warkentin TE, Crowther MA, Kelton JG. FcγRIIa proteolysis as a diagnostic biomarker for heparin-induced thrombocytopenia. J Thromb Haemost 2013; 11:1146-53. [PMID: 23551961 DOI: 10.1111/jth.12208] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2012] [Indexed: 11/28/2022]
Abstract
BACKGROUND A significant challenge in the management of heparin-induced thrombocytopenia (HIT) patients is making a timely and accurate diagnosis. The readily available enzyme immunoassays (EIAs) have low specificities. In contrast, platelet activation assays have higher specificities, but they are technically demanding and not widely available. In addition, ~ 10% of samples referred for HIT testing are initially classified as indeterminate by the serotonin release assay (SRA), which further delays accurate diagnosis. HIT is characterized by platelet activation, which leads to FcγRIIa proteolysis. This raises the possibility that identification of the proteolytic fragment of FcγRIIa could serve as a surrogate marker for HIT. OBJECTIVES To determine the specificity of platelet FcγRIIa proteolysis induced by sera from patients with HIT, and to correlate the results with those of the SRA. METHODS/PATIENTS Sera from HIT patients and control patients with other thrombocytopenic/prothrombotic disorders were tested for their ability to proteolyse FcγRIIa. The results were correlated with anti-platelet factor 4 (PF4)/heparin antibodies (EIA), and heparin-dependent platelet activation (SRA). RESULTS Only HIT patient samples (20/20) caused heparin-dependent FcγRIIa proteolysis, similar to what was shown by the SRA. None of the samples from the other patient groups or hospital controls caused FcγRIIa proteolysis. Among nine additional samples that tested indeterminate in the SRA, FcγRIIa proteolysis resolved five samples that had a positive anti-PF4/heparin EIA result; three had no FcγRIIa proteolysis, and two were shown to have heparin-dependent FcγRIIa proteolysis CONCLUSIONS This study suggests that heparin-dependent FcγRIIa proteolysis is at least as specific as the SRA for the diagnosis of HIT.
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Affiliation(s)
- I Nazi
- Department of Medicine, Michael G DeGroote School of Medicine, McMaster University, Hamilton, Ontario, Canada.
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Bakchoul T, Greinacher A. Recent advances in the diagnosis and treatment of heparin-induced thrombocytopenia. Ther Adv Hematol 2013; 3:237-51. [PMID: 23606934 DOI: 10.1177/2040620712443537] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Heparin-induced thrombocytopenia (HIT) is a drug-mediated, prothrombotic disorder caused by immunization against platelet factor 4 (PF4) after complex formation with heparin or other polyanions. After their binding to PF4/heparin complexes on the platelet surface, HIT antibodies are capable of intravascular platelet activation by cross-linking Fcγ receptor IIA leading to a platelet count decrease and/or thrombosis. Diagnosis of HIT is often difficult. This, and the low specificity of the commercially available immunoassays, leads currently to substantial overdiagnosis of HIT. Timing of onset, the moderate nature of thrombocytopenia, and the common concurrence of thrombosis are very important factors, which help to differentiate HIT from other potential causes of thrombocytopenia. A combination of a clinical pretest scoring system and laboratory investigation is usually necessary to diagnose HIT. Although HIT is considered to be a rare complication of heparin treatment, the very high number of hospital inpatients, and increasingly also hospital outpatients receiving heparin, still result in a considerable number of patients developing HIT. If HIT occurs, potentially devastating complications such as life-threatening thrombosis make it one of the most serious adverse drug reactions. If HIT is strongly suspected, all heparin must be stopped and an alternative nonheparin anticoagulant started at a therapeutic dose to prevent thromboembolic complications. However, the nonheparin alternative anticoagulants bear a considerable bleeding risk, especially if given to patients with thrombocytopenia due to other reasons than HIT. While established drugs for HIT are disappearing from the market (lepirudin, danaparoid), bivalirudin, fondaparinux and potentially the new anticoagulants such as dabigatran, rivaroxaban and apixaban provide new treatment options.
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Affiliation(s)
- Tamam Bakchoul
- Department of Immunology and Transfusion Medicine, Ernst-Moritz-Arndt niversity, Greifswald, Germany
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Althaus K, Hron G, Strobel U, Abbate R, Rogolino A, Davidson S, Greinacher A, Bakchoul T. Evaluation of automated immunoassays in the diagnosis of heparin induced thrombocytopenia. Thromb Res 2013; 131:e85-90. [DOI: 10.1016/j.thromres.2013.01.005] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2012] [Revised: 12/10/2012] [Accepted: 01/02/2013] [Indexed: 10/27/2022]
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Heparin-Induced Thrombocytopenia. Platelets 2013. [DOI: 10.1016/b978-0-12-387837-3.00042-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Warkentin TE, Greinacher A, Gruel Y, Aster RH, Chong BH. Laboratory testing for heparin-induced thrombocytopenia: a conceptual framework and implications for diagnosis. J Thromb Haemost 2011; 9:2498-500. [PMID: 22947414 DOI: 10.1111/j.1538-7836.2011.04536.x] [Citation(s) in RCA: 142] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
- T E Warkentin
- Department of Pathology and Molecular Medicine and Department of Medicine, McMaster University, Hamilton, Canada.
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Warkentin TE. How I diagnose and manage HIT. HEMATOLOGY. AMERICAN SOCIETY OF HEMATOLOGY. EDUCATION PROGRAM 2011; 2011:143-149. [PMID: 22160026 DOI: 10.1182/asheducation-2011.1.143] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Heparin-induced thrombocytopenia (HIT) is a prothrombotic drug reaction caused by platelet-activating IgG antibodies that recognize platelet factor 4 (PF4)/polyanion complexes. Platelet activation assays, such as the serotonin-release assay, are superior to PF4-dependent immunoassays in discerning which heparin-induced antibodies are clinically relevant. When HIT is strongly suspected, standard practice includes substituting heparin with an alternative anticoagulant; the 2 US-approved agents are the direct thrombin inhibitors (DTIs) lepirudin and argatroban, which are "niche" agents used only to manage HIT. However, only ~ 10% of patients who undergo serological investigation for HIT actually have this diagnosis. Indeed, depending on the clinical setting, only 10%-50% of patients with positive PF4-dependent immunoassays have platelet-activating antibodies. Therefore, overdiagnosis of HIT can be minimized by insisting that a positive platelet activation assay be required for definitive diagnosis of HIT. For these reasons, a management strategy that considers the real possibility of non-HIT thrombocytopenia is warranted. One approach that I suggest is to administer an indirect, antithrombin (AT)-dependent factor Xa inhibitor (danaparoid or fondaparinux) based upon the following rationale: (1) effectiveness in treating and preventing HIT-associated thrombosis; (2) effectiveness in treating and preventing thrombosis in diverse non-HIT situations; (3) both prophylactic- and therapeutic-dose protocols exist, permitting dosing appropriate for the clinical situation; (4) body weight-adjusted dosing protocols and availability of specific anti-factor Xa monitoring reduce risk of under- or overdosing (as can occur with partial thromboplastin time [PTT]-adjusted DTI therapy); (5) their long half-lives reduce risk of rebound hypercoagulability; (6) easy coumarin overlap; and (7) relatively low cost.
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Affiliation(s)
- Theodore E Warkentin
- Department of Pathology and Molecular Medicine, Michael G DeGroote School of Medicine, McMaster University, Hamilton, ON, Canada.
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