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Abstract
Laboratory testing for heparin-induced thrombocytopenia (HIT) has important shortcomings. Immunoassays fail to discriminate platelet-activating from nonpathogenic antibodies. Specific functional assays are impracticable due to the need for platelets and radioisotope. We describe 2 assays that may overcome these limitations. The KKO-inhibition test (KKO-I) measures the effect of plasma on binding of the HIT-like monoclonal antibody KKO to platelet factor 4 (PF4)/heparin. DT40-luciferase (DT40-luc) is a functional test comprised of a B-cell line expressing FcγRIIa coupled to a luciferase reporter. We compared these assays to polyspecific and immunoglobulin (Ig)G-specific PF4/heparin enzyme-linked immunosorbent assays (ELISAs) in samples from 58 patients with suspected HIT and circulating anti-PF4/heparin antibodies. HIT was defined as a 4Ts score ≥ 4 and positive (14)C-serotonin release assay. HIT-positive plasma demonstrated greater mean inhibition of KKO binding than HIT-negative plasma (78.9% vs 26.0%; P < .0001) and induced greater luciferase activity (3.14-fold basal vs 0.96-fold basal; P < .0001). The area under the receiver-operating characteristic curve was greater for KKO-I (0.93) than for the polyspecific (0.82; P = .020) and IgG-specific ELISA (0.76; P = .0044) and for DT40-luc (0.89) than for the IgG-specific ELISA (P = .046). KKO-I and DT40-luc showed better discrimination than 2 commercially available immunoassays, are simple to perform, and hold promise for improving the specificity and feasibility of HIT laboratory testing.
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52
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Craik JD, Cobb AG. Heparin-induced thrombocytopenia following hip and knee arthroplasty. Br J Haematol 2013; 161:255-61. [PMID: 23406088 DOI: 10.1111/bjh.12242] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2012] [Accepted: 12/30/2012] [Indexed: 12/19/2022]
Abstract
Until recently, both the British Society for Haematology and American College of Chest Physicians recommended platelet monitoring in all surgical patients receiving prophylactic low molecular weight heparin (LMWH) for the early diagnosis of heparin-induced thrombocytopenia (HIT). These guidelines were reversed in 2012 based upon an analysis considering resource expenditure, assay result timeframes, and complications relating to HIT treatment. However, there are no large studies reviewing lower limb arthroplasty patients on an individual basis to determine the incidence of HIT in this patient group. This study investigated 10 797 patients who underwent primary hip or knee arthroplasty with LMWH prophylaxis over a 5 years period. 32·6% of patients (n = 3515) had platelet counts recorded up to 14 d postoperatively with 13 patients (0·37%) developing thrombocytopenia. Platelet counts recovered spontaneously in five patients, and two patients had other identifiable causes. Only one of the remaining six patients developed thrombosis indicating an incidence of HIT-related thrombosis of 0·03%. The potential for identifying HIT with platelet monitoring in patients receiving LMWH prophylaxis is low and therefore routine monitoring for HIT is not justified.
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Affiliation(s)
- Johnathan D Craik
- The Elective Orthopaedic Centre, Epsom General Hospital, Epsom, Surrey, UK.
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53
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Lee GM, Arepally GM. Heparin-induced thrombocytopenia. HEMATOLOGY. AMERICAN SOCIETY OF HEMATOLOGY. EDUCATION PROGRAM 2013; 2013:668-74. [PMID: 24319250 PMCID: PMC4153428 DOI: 10.1182/asheducation-2013.1.668] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Heparin-induced thrombocytopenia (HIT) is a prothrombotic disorder caused by antibodies that recognize complexes of platelet factor 4 (PF4) and heparin. HIT is frequently considered in the differential diagnosis of thrombocytopenia occurring in patients on heparin therapy. HIT is a challenging diagnosis because of routine heparin use in hospitalized patients, the common occurrence of thrombocytopenia, and high rates of anti-PF4/heparin seroconversions in patients treated with heparin. Our diagnostic approach to HIT is presented here, underscoring critical elements of clinical and laboratory evaluation.
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Affiliation(s)
- Grace M. Lee
- Hematology/Oncology Fellow, Division of Hematology, Department of Medicine, DUMC Box 3841, Duke University Medical Center, Room 301 Sands Building, Durham, NC 27710, Phone: 919-668-1550, Fax: 919-684-2420
| | - Gowthami M. Arepally
- Associate Professor, Medicine, Division of Hematology, Department of Medicine, Duke University Medical Center, DUMC Box 3486, Room 301 Sands Building, Durham, NC 27710, Phone: 919-668-1550, Fax: 919-684-2420
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54
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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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55
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Zhou A, Winkler A, Emamifar A, Gartland B, Duncan A, Antun A, Arellano M, Tindol GA, Levy JH, Bornstein WA, Horowitz IR, Khoury HJ. Is the Incidence of Heparin-Induced Thrombocytopenia Affected by the Increased Use of Heparin for VTE Prophylaxis? Chest 2012; 142:1175-1178. [DOI: 10.1378/chest.11-2926] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
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Predictive value of the 4Ts scoring system for heparin-induced thrombocytopenia: a systematic review and meta-analysis. Blood 2012; 120:4160-7. [PMID: 22990018 DOI: 10.1182/blood-2012-07-443051] [Citation(s) in RCA: 289] [Impact Index Per Article: 24.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The 4Ts is a pretest clinical scoring system for heparin-induced thrombocytopenia (HIT). Although widely used in clinical practice, its predictive value for HIT in diverse settings and patient populations is unknown. We performed a systematic review and meta-analysis to estimate the predictive value of the 4Ts in patients with suspected HIT. We searched PubMed, Cochrane Database, and ISI Web of Science for studies that included patients with suspected HIT, who were evaluated by both the 4Ts and a reference standard against which the 4Ts could be compared. Quality of eligible studies was assessed by QUADAS-2 criteria. Thirteen studies, collectively involving 3068 patients, fulfilled eligibility criteria. A total of 1712 (55.8%) patients were classified by 4Ts score as having a low probability of HIT. The negative predictive value of a low probability 4Ts score was 0.998 (95% CI, 0.970-1.000) and remained high irrespective of the party responsible for scoring, the prevalence of HIT, or the composition of the study population. The positive predictive value of an intermediate and high probability 4Ts score was 0.14 (0.09-0.22) and 0.64 (0.40-0.82), respectively. A low probability 4Ts score appears to be a robust means of excluding HIT. Patients with intermediate and high probability scores require further evaluation.
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57
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Abstract
Prevailing approaches to manage autoimmune thrombotic disorders, such as heparin-induced thrombocytopenia, antiphospholipid syndrome and thrombotic thrombocytopenic purpura, include immunosuppression and systemic anticoagulation, though neither provides optimal outcome for many patients. A different approach is suggested by the concurrence of autoantibodies and their antigenic targets in the absence of clinical disease, such as platelet factor 4 in heparin-induced thrombocytopenia and β(2)-glycoprotein-I (β(2)GPI) in antiphospholipid syndrome. The presence of autoantibodies in the absence of disease suggests that conformational changes or other alterations in endogenous protein autoantigens are required for recognition by pathogenic autoantibodies. In thrombotic thrombocytopenic purpura, the clinical impact of ADAMTS13 deficiency caused by autoantibodies likely depends on the balance between residual antigen, that is, enzyme activity, and demand imposed by local genesis of ultralarge multimers of von Willebrand factor. A corollary of these concepts is that disrupting platelet factor 4 and β(2)GPI conformation (or ultralarge multimer of von Willebrand factor oligomerization or function) might provide a disease-targeted approach to prevent thrombosis without systemic anticoagulation or immunosuppression. Validation of this approach requires a deeper understanding of how seemingly normal host proteins become antigenic or undergo changes that increase antibody avidity, and how they can be altered to retain adaptive functions while shedding epitopes prone to elicit harmful autoimmunity.
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58
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Bloemen A, Testroote MJG, Janssen-Heijnen MLG, Janzing HMJ. Incidence and diagnosis of heparin-induced thrombocytopenia (HIT) in patients with traumatic injuries treated with unfractioned or low-molecular-weight heparin: a literature review. Injury 2012; 43:548-52. [PMID: 21640991 DOI: 10.1016/j.injury.2011.05.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/14/2010] [Revised: 04/17/2011] [Accepted: 05/09/2011] [Indexed: 02/02/2023]
Abstract
INTRODUCTION The incidence of thromboembolic complications after major traumatic injuries is high (>50%). Thromboprophylaxis, often by low-molecular-weight heparin (LMWH) or unfractioned heparin (UH) is therefore routinely administered. Thromboprophylaxis is also advised after immobilisation for isolated lower leg injuries. Heparin induced thrombocytopenia (HIT) is a rare but very serious immune mediated complication of treatment with LMWH, which can cause potentially fatal thromboembolism. In the general medical and surgical population the incidence of HIT is 0.2%. Little is known about the incidence of HIT and value of screening in trauma patients and in isolated lower extremity injuries. Therefore, we performed a systematic literature review. METHODS The online databases Medline and EMBASE were searched independently by two authors. Manuscripts were selected for analysis by quantitative and qualitative selection. After eliminating duplicate articles and irrelevant studies, seven relevant papers reporting on the incidence of HIT in trauma patients were identified and two studies reported the incidence of HIT in patients with lower leg injuries. RESULTS The selected papers varied in study design: three randomised controlled trials, three cohort studies and one case report were identified. The methodological quality of the studies varied. In a total population of 1920 patients, HIT was identified in seven patients (0.36%). Pooling of data was impossible due to heterogeneity in study design and populations. No HIT was reported in 826 patients with lower extremity injuries, requiring immobilisation. DISCUSSION Only a few studies have reported on the incidence of HIT in trauma patients who receive prophylactic LMWH. In the heterogenous populations of the available studies, the incidence of HIT appears to be very low and comparable to other patient populations. There is hardly any literature on the incidence of HIT in patients with isolated lower leg injuries receiving LMWH, but incidence seems to be very low. CONCLUSION The incidence of HIT in trauma patients who receive LMWH thromboprophylaxis appears to be low (0.36%). Incidence of HIT in patients with isolated lower leg injuries receiving LMWH seems very low. Monitoring of platelet count could be considered in hospitalised patients with a high risk for development of HIT. A pre-test scoring system may identify these patients.
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Affiliation(s)
- A Bloemen
- Department of Surgery and Orthopaedic Surgery, VieCuri Medical Centre, Tegelseweg 210, 5912 BL Venlo, The Netherlands
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59
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Recognition of heparin-induced thrombocytopenia and initiation of argatroban therapy after cardiothoracic surgery in the intensive care unit. J Thorac Cardiovasc Surg 2012; 143:1213-8. [DOI: 10.1016/j.jtcvs.2011.07.068] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Revised: 06/05/2011] [Accepted: 07/19/2011] [Indexed: 11/19/2022]
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60
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Linkins LA, Dans AL, Moores LK, Bona R, Davidson BL, Schulman S, Crowther M. Treatment and prevention of heparin-induced thrombocytopenia: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest 2012; 141:e495S-e530S. [PMID: 22315270 DOI: 10.1378/chest.11-2303] [Citation(s) in RCA: 617] [Impact Index Per Article: 51.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND Heparin-induced thrombocytopenia (HIT) is an antibody-mediated adverse drug reaction that can lead to devastating thromboembolic complications, including pulmonary embolism, ischemic limb necrosis necessitating limb amputation, acute myocardial infarction, and stroke. METHODS The methods of this guideline follow the Methodology for the Development of Antithrombotic Therapy and Prevention of Thrombosis Guidelines: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines in this supplement. RESULTS Among the key recommendations for this article are the following: For patients receiving heparin in whom clinicians consider the risk of HIT to be > 1%, we suggest that platelet count monitoring be performed every 2 or 3 days from day 4 to day 14 (or until heparin is stopped, whichever occurs first) (Grade 2C). For patients receiving heparin in whom clinicians consider the risk of HIT to be < 1%, we suggest that platelet counts not be monitored (Grade 2C). In patients with HIT with thrombosis (HITT) or isolated HIT who have normal renal function, we suggest the use of argatroban or lepirudin or danaparoid over other nonheparin anticoagulants (Grade 2C). In patients with HITT and renal insufficiency, we suggest the use of argatroban over other nonheparin anticoagulants (Grade 2C). In patients with acute HIT or subacute HIT who require urgent cardiac surgery, we suggest the use of bivalirudin over other nonheparin anticoagulants or heparin plus antiplatelet agents (Grade 2C). CONCLUSIONS Further studies evaluating the role of fondaparinux and the new oral anticoagulants in the treatment of HIT are needed.
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Affiliation(s)
- Lori-Ann Linkins
- Department of Medicine, McMaster University, Hamilton, ON, Canada.
| | - Antonio L Dans
- College of Medicine, University of the Philippines Manila, Manila, Philippines
| | - Lisa K Moores
- The Uniformed Services, University of Health Sciences, Bethesda, MD
| | - Robert Bona
- School of Medicine, Quinnipiac University, North Haven, CT
| | | | - Sam Schulman
- Department of Medicine, McMaster University, Hamilton, ON, Canada
| | - Mark Crowther
- Department of Medicine, McMaster University, Hamilton, ON, Canada
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61
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Abstract
BACKGROUND Heparin-induced thrombocytopenia (HIT) is a rare but severe prothrombotic adverse effect of heparin treatment. The underlying cause is the formation of highly immunogenic complexes between negatively charged heparin and positively charged platelet factor 4 (PF4). Resulting antibodies against these PF4/heparin complexes can activate platelets via the platelet FcγIIa receptor, leading to thrombin generation and thus to the paradox of a prothrombotic state despite thrombocytopenia and application of heparin. Prompt diagnosis of HIT is important in order to change treatment to prevent severe thromboembolic complications. However, this is often difficult as thrombocytopenia is frequent in hospitalized patients and the commercially available laboratory tests for HIT antibodies have a high negative predictive value but only a poor positive predictive value. This leads to overdiagnosis and overtreatment of HIT, which also bear the risk for adverse outcomes. AREAS COVERED This review aims at resuming recent data on HIT, thereby focusing on the role of new anticoagulants and providing a framework for diagnosis and treatment. Furthermore, it provides some insights into the pathogenesis of this peculiar adverse drug reaction and ventures a guess at its future relevance in clinical practice. EXPERT OPINION New drugs which are strongly negatively charged should be assessed for their capacity to form complexes with PF4. If they do so, they bear the risk of inducing a HIT-like immune response. The immunology of HIT is still largely unresolved. Understanding HIT might provide insights into other immune and autoimmune response mechanisms.
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Affiliation(s)
- Miriam E Jaax
- Institute for Immunology and Transfusion Medicine, University Medicine Ernst Moritz Arndt University Greifswald, Sauerbruchstrasse, 17487 Greifswald, Germany
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62
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VAN HOECKE F, DEVREESE K. Evaluation of two new automated chemiluminescent assays (HemosIL®AcuStar HIT-IgG and HemosIL®AcuStar HIT-Ab) for the detection of heparin-induced antibodies in the diagnosis of heparin-induced thrombocytopenia. Int J Lab Hematol 2012; 34:410-6. [DOI: 10.1111/j.1751-553x.2012.01413.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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63
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Wanat M, Fitousis K, Hall J, Rice L. PF4/heparin antibody testing and treatment of heparin-induced thrombocytopenia in the intensive care unit. Clin Appl Thromb Hemost 2012; 19:297-302. [PMID: 22387583 DOI: 10.1177/1076029612438709] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND The diagnosis of heparin-induced thrombocytopenia (HIT) may be challenging in critically ill patients, as heparin exposures are ubiquitous, and thrombocytopenia is common. Unwarranted ordering and incorrect interpretation of heparin antibody tests can expose a patient to adverse drug events and imposes a significant economic burden on our health care system. METHODS A prospective, observational study was performed over 4 months on all adult patients located in 5 intensive care units, with a heparin antibody test ordered. RESULTS A platelet factor 4/heparin enzyme-linked immunosorbent assay (ELISA) test was ordered in 131 patients. In total, 110 patients had a low 4Ts score (0-3), and of these 103 had a negative ELISA result. In patients with a low 4Ts score, 0 (0%) of 110 had an optical density value >1.0. One hundred twenty-nine patients (98%) had another possible cause of thrombocytopenia identified. CONCLUSION In critically ill patients, low 4Ts scores indicate a low probability of HIT, and heparin antibody testing in these patients is not useful.
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Affiliation(s)
- Matthew Wanat
- Department of Pharmacy, The Methodist Hospital, Houston, TX 77030,
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64
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Tanimura K, Ebina Y, Sonoyama A, Morita H, Miyata S, Yamada H. Argatroban therapy for heparin-induced thrombocytopenia during pregnancy in a woman with hereditary antithrombin deficiency. J Obstet Gynaecol Res 2012; 38:749-52. [DOI: 10.1111/j.1447-0756.2011.01758.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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65
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Abstract
Heparin-induced thrombocytopenia is a prothrombotic adverse drug effect induced by platelet-activating antibodies against multimolecular complexes of platelet factor 4 and heparin. Diagnosis rests on a clinical assessment of disease probability and laboratory testing. Management involves immediate discontinuation of heparin and initiation of an alternative anticoagulant. Because of the frequency of thrombocytopenia among heparinized patients, the limited specificity of widely available immunoassays, the limited availability of more specific functional assays, and clinicians' fears of missing a case of true disease, overtesting, overdiagnosis, and overtreatment have become common. As a result, a substantial number of thrombocytopenic patients are unnecessarily exposed to costly alternative anticoagulants and their attendant risk of bleeding. In this review, we describe not only our approach to the evaluation and management of patients with heparin-induced thrombocytopenia, but also the measures we use to minimize misdiagnosis and unnecessary treatment of patients without the disease. In addition, we propose areas of investigation for improvement of the diagnosis and management of this potentially fatal disorder.
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66
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Thrombosis in suspected heparin-induced thrombocytopenia occurs more often with high antibody levels. Am J Med 2012; 125:44-9. [PMID: 22075045 DOI: 10.1016/j.amjmed.2011.06.025] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/14/2011] [Revised: 06/26/2011] [Accepted: 06/27/2011] [Indexed: 11/23/2022]
Abstract
OBJECTIVE The study objective was to determine whether higher antiplatelet factor 4 (PF4)/heparin antibody levels using an enzyme-linked immunosorbent assay are associated with more frequent thrombotic events in patients with clinically suspected heparin-induced thrombocytopenia. Heparin-induced thrombocytopenia is an immune-mediated adverse drug reaction. An enzyme-linked immunosorbent assay detects anti-PF4/heparin antibodies to support a suspected clinical diagnosis of heparin-induced thrombocytopenia. The utility of quantitative enzyme-linked immunosorbent assay results is uncertain. METHODS Our single-centered study evaluated quantitative anti-PF4/heparin antibody levels using an enzyme-linked immunosorbent assay in consecutive hospitalized patients with a clinical suspicion of heparin-induced thrombocytopenia and positive anti-PF4/heparin antibody levels between July 2003 and December 2006. RESULTS Overall, anti-PF4/heparin antibody values were available for 318 patients with clinically suspected heparin-induced thrombocytopenia. The median level was 0.85 optical density units (range 0.31-4.0). The overall rate of arterial or venous thrombosis was 23.3%. A 1-unit increase in anti-PF4/heparin antibody level was associated with an approximate doubling in the odds of thrombosis by 30 days (odds ratio, 1.9; 95% confidence interval, 1.5-2.6; P=.0001). The proportion of patients with pulmonary embolism increased with higher anti-PF4/heparin antibody levels. CONCLUSION Higher levels of anti-PF4/heparin antibody are associated with increased thrombosis risk among patients with clinically suspected heparin-induced thrombocytopenia and might have clinical utility for prediction of true heparin-induced thrombocytopenia and the development of thrombosis.
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67
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Results of a consensus meeting on the use of argatroban in patients with heparin-induced thrombocytopenia requiring antithrombotic therapy - a European Perspective. Thromb Res 2011; 129:426-33. [PMID: 22178575 DOI: 10.1016/j.thromres.2011.11.041] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Revised: 11/22/2011] [Accepted: 11/24/2011] [Indexed: 02/07/2023]
Abstract
Argatroban has been introduced as an alternative parenteral anticoagulant for HIT-patients in several European countries in 2005. In 2009 a panel of experts discussed their clinical experience with argatroban balancing risks and benefits of argatroban treatment in managing the highly procoagulant status of HIT-patients. This article summarizes the main conclusions of this round table discussion. An ongoing issue is the appropriate dosing of argatroban in special patient groups. Therefore, dosing recommendations for different HIT-patient groups (ICU patients; non-ICU patients, paediatric patients, and for patients undergoing renal replacement therapies) are summarized in this consensus statement. Because of the strong correlation between argatroban dosing requirements and scores used to characterize the severity of illness (APACHE; SAPS, SOFA) suitable dosing nomograms are given. This consensus statement contributes to clinically relevant information on the appropriate use and monitoring of argatroban based on the current literature, and provides additional information from clinical experience. As the two other approved drugs for HIT, danaparoid and lepirudin are either currently not available due to manufacturing problems (danaparoid) or will be withdrawn from the market in 2012 (lepirudin), this report should guide physicians who have limited experience with argatroban how to use this drug safely in patients with HIT.
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68
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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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Najaoui A, Bakchoul T, Stoy J, Bein G, Rummel MJ, Santoso S, Sachs UJ. Autoantibody-mediated complement activation on platelets is a common finding in patients with immune thrombocytopenic purpura (ITP). Eur J Haematol 2011; 88:167-74. [PMID: 21985182 DOI: 10.1111/j.1600-0609.2011.01718.x] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
BACKGROUND It is commonly accepted that antibody-mediated removal of platelets represents a major mechanism of platelet destruction in immune thrombocytopenic purpura (ITP). Although complement activation may participate in platelet clearance, frequency and specificity of complement activation have not yet been studied systematically in ITP. PATIENTS AND METHODS We examined blood samples from 240 patients with ITP. Samples were assessed for the presence of free and bound platelet autoantibodies by a standard glycoprotein-specific assay (monoclonal antibody-specific immobilization of platelet antigens). The ability of all sera to fix complement to a panel of human platelets was investigated in a complement fixation (CF) assay. Fixation of C1q to isolated GP IIb/IIIa was assessed by flow cytometry. RESULTS Glycoprotein-specific autoantibodies were detected as platelet-bound antibodies in 129 (54%) and as additional free antibodies in 26 (11%) and were undetectable in 111 (46%) patients. Assessing these subgroups for CF, 103 (65%), 21 (81%), and 33 (30%) sera gave positive results. If GP IIb/IIIa was absent from the test platelets, 81 (67%) lost their ability to fix complement; if GP Ib/IX was absent, 37 (30%) lost their ability to fix complement. C1q fixation to immunobeads coated with GP IIb/IIIa was observed in 50% of sera containing anti-GP IIb/IIIa antibodies. CONCLUSIONS In a significant number of patients with chronic ITP, platelet autoantibodies are capable of activating the classical complement pathway. CF is even present in ITP sera without detectable autoantibodies, indicating that current techniques for autoantibody detection may be insufficient. The major targets for complement-fixing autoantibodies in ITP are GP IIb/IIIa and GP Ib/IX.
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Affiliation(s)
- Abderrahim Najaoui
- Institute for Clinical Immunology and Transfusion Medicine, Justus Liebig University, Giessen, Germany
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70
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Radaideh SM, Frenkel EP, Dowell JE, Sarode R, Shen YM. Incidence of Isolated Heparin-Induced Thrombocytopenia and Risk of Thrombosis by IgG-Specific Anti-PF4/Heparin ELISA. Clin Appl Thromb Hemost 2011; 18:215-7. [DOI: 10.1177/1076029611423389] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Heparin-induced thrombocytopenia (HIT) antibodies are screened by an enzyme-linked immunosorbent assay (ELISA). Polyspecific ELISA detects anti-PF4/heparin IgG, IgA, and IgM. Recently, anti-PF4/heparin IgG ELISA has been shown to be more specific. However, the impact of using the IgG-ELISA on the incidence of isolated HIT (thrombocytopenia alone without clinically evident thrombosis) and the risk of developing subsequent thrombosis are still unknown. Methods: A total of 492 consecutive patients with clinically suspected HIT at The University of Texas Southwestern Medical Center and affiliated hospitals were retrospectively reviewed from December 2008 to May 2010. RESULTS: 29 patients (6%) were diagnosed with HIT based on clinical findings and positive ELISA. 19 of the 29 patients (65%) had thrombosis at the time of diagnosis; whereas 10 of the 29 (35%) had only isolated HIT. The ten patients with isolated HIT had serial follow up for at least 3 months. 3 of 10 were treated with direct thrombin inhibitors and 5 of 10 were treated with Warfarin for at least 1 month upon discharge. None of them developed symptoms or signs of thrombosis during 3 months of follow up. Conclusion: The incidence of isolated HIT in this study was 35%, which is significantly lower than previously reported in the literature. It is possible that some patients previously thought to have HIT by the poly-specific ELISA assay had false positive results. The improved specificity of the IgG- ELISA appears to reduce the incidence of isolated HIT which may have lower risk of subsequent thrombosis.
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Affiliation(s)
- Sofyan M. Radaideh
- Division of Hematology/Oncology, Department of Medicine, UT Southwestern Medical Center at Dallas, Dallas, TX, USA
| | - Eugene P. Frenkel
- Division of Hematology/Oncology, Department of Medicine, UT Southwestern Medical Center at Dallas, Dallas, TX, USA
| | - Jonathan E. Dowell
- Division of Hematology/Oncology, Department of Medicine, UT Southwestern Medical Center at Dallas, Dallas, TX, USA
| | - Ravindra Sarode
- Department of Pathology, UT Southwestern Medical Center at Dallas, Dallas, TX, USA
| | - Yu-Min Shen
- Division of Hematology/Oncology, Department of Medicine, UT Southwestern Medical Center at Dallas, Dallas, TX, USA
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Hu P, Fang L, Jones CM, Chess EK. Collective sampling of intact anionic polysaccharide components and application in quantitative determination by LC-MS. Carbohydr Res 2011; 346:2268-73. [PMID: 21867994 DOI: 10.1016/j.carres.2011.07.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2011] [Revised: 07/01/2011] [Accepted: 07/19/2011] [Indexed: 11/27/2022]
Abstract
Anionic polysaccharides, such as glycosaminoglycans (GAGs) and alginate, readily undergo source-induced fragmentation when analyzed by electrospray mass spectrometry with the use of high source cone voltage. The dissociation chemistry converts all components of a polysaccharide into a small set of structurally characteristic small saccharides. This chemistry enables the collective detection of a polysaccharide through the detection of one or more small saccharides. This ability, combined with the elution of polysaccharides as relatively compact bands using ion-pairing reverse phase liquid chromatography, created a unique opportunity for the development of LC-MS methods suitable for the quantitative analysis of intact anionic polysaccharides. Feasibility of this approach is demonstrated with a mixture of heparin, chondroitin sulfate A, and alginate.
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Affiliation(s)
- Peifeng Hu
- Technology Resources, Baxter Healthcare Corporation, 25212 W. Illinois Route 120, Round Lake, IL 60073, USA.
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Nellen V, Sulzer I, Barizzi G, Lämmle B, Alberio L. Rapid exclusion or confirmation of heparin-induced thrombocytopenia: a single-center experience with 1,291 patients. Haematologica 2011; 97:89-97. [PMID: 21933856 DOI: 10.3324/haematol.2011.048074] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND The current gold-standard for diagnosing heparin-induced thrombocytopenia is the detection of platelet-activating antibodies by means of functional assays which, since they are time consuming and not widely available, are not suited to guiding acute treatment decisions. The objective of our study was to assess the ability of more rapid immunoassays to predict the presence of functionally relevant anti-platelet factor 4/heparin-antibodies. DESIGN AND METHODS We analyzed 1,291 of 1,383 (93.4%) patients consecutively evaluated for suspected heparin-induced thrombocytopenia at our institution. Clinical pre-test probability was defined by the 4T-score. Anti-platelet factor 4/heparin-antibodies were measured with three immunoassays (ID-H/PF4-PaGIA, Asserachrom-HPIA, and GTI-PF4) and their functional relevance was assessed by a two-point heparin-induced platelet aggregation test. Performance of the immunoassays was evaluated by receiver operating characteristic analysis. RESULTS Among 1,291 patients, 96 (7.4%) had a positive heparin-induced platelet aggregation-test: 7 of 859 (0.8%) with a low, 50 of 358 (14.0%) with an intermediate, and 39 of 74 (52.7%) with a high 4T-score. Receiver operating characteristics analysis indicated that best immunoassay thresholds for predicting a positive platelet aggregation test were: Titer of 4 or more (ID-H/PF4-PaGIA), optical density more than 0.943 (Asserachrom-HPIA) and more than 1.367 (GTI-PF4). A 100% negative predictive value was observed at the following thresholds: Titer of 1 or under (ID-H/PF4-PaGIA), optical density less than 0.300 (Asserachrom-HPIA) and less than 0.870 (GTI-PF4). A 100% positive predictive value was reached only by ID-H/PF4-PaGIA, at titers of 32 or over. Positive and negative likelihood ratios were calculated for results between the thresholds with 100% negative or positive predictive value. CONCLUSIONS We show that: i) negative and weak positive results of immunoassays detecting anti-platelet factor 4/heparin-antibodies exclude heparin-induced thrombocytopenia; ii) anti-platelet factor 4/heparin-antibody titers of 32 or over (ID-H/PF4-PaGIA) have a 100% positive predictive value for functionally relevant antibodies; iii) combining the clinical pre-test probability with the likelihood ratio of intermediate immunoassay results allows assessment of post-test probability for heparin-induced thrombocytopenia in individual patients.
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Affiliation(s)
- Vanessa Nellen
- Department of Haematology, Central Haematology Laboratory, Inselspital, Bern University Hospital and University of Bern, Switzerland
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74
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Althaus K, Strobel U, Warkentin TE, Greinacher A. Combined use of the high heparin step and optical density to optimize diagnostic sensitivity and specificity of an anti-PF4/heparin enzyme-immunoassay. Thromb Res 2011; 128:256-60. [DOI: 10.1016/j.thromres.2011.05.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2011] [Revised: 04/12/2011] [Accepted: 05/02/2011] [Indexed: 10/18/2022]
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Yoshika M, Komiyama Y, Hirakawa A, Nakatani T, Takahashi H. A Difficult Diagnosis Case of Prolonged Thrombocytopenia With Sepsis and Disseminated Intravascular Coagulation. Clin Appl Thromb Hemost 2011; 17:410-3. [DOI: 10.1177/1076029610371473] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
A 19-year-old male was admitted because of the trauma due to sepsis-induced disseminated intravascular coagulation (DIC) and multiple organ failure (MOF). We treated with antibiotics, danaparoid, and continuous hemodiafiltration (CHDF). Once he recovered, but after several days, he had septic shock and MOF again. With treatment, the inflammation and MOF improved but the platelet count was less than 1.0 × 10 4/μL. Because of the usage of heparin, we suspected heparin-induced thrombocytopenia (HIT) and measured the HIT antibody and a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13). Heparin-induced thrombocytopenia antibody was positive in the second sepsis but negative in the first sepsis. ADAMTS13 activity was low in both sepses. After stopping CHDF and the usage of heparin, his platelet count improved. Thrombocytopenia is the common and occasional condition for DIC. Heparin-induced thrombocytopenia and thrombotic thrombocytopenic purpura is rare but they must be ruled out in thrombocytopenia with nontypical clinical course, and the assays for HIT antibody and ADAMTS13 activity are useful tools.
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Affiliation(s)
- Masamichi Yoshika
- Department of Clinical Sciences and Laboratory Medicine, Kansai Medical University, Moriguchi, Osaka, Japan,
| | - Yutaka Komiyama
- Department of Clinical Sciences and Laboratory Medicine, Kansai Medical University, Moriguchi, Osaka, Japan
| | - Akihiko Hirakawa
- Department of Emergency and Critical Care Medicine, Kansai Medical University Takii Hospital, Moriguchi, Osaka, Japan
| | - Toshio Nakatani
- Department of Emergency and Critical Care Medicine, Kansai Medical University Takii Hospital, Moriguchi, Osaka, Japan
| | - Hakuo Takahashi
- Department of Clinical Sciences and Laboratory Medicine, Kansai Medical University, Moriguchi, Osaka, Japan
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Demma LJ, Winkler AM, Levy JH. A diagnosis of heparin-induced thrombocytopenia with combined clinical and laboratory methods in cardiothoracic surgical intensive care unit patients. Anesth Analg 2011; 113:697-702. [PMID: 21788317 DOI: 10.1213/ane.0b013e3182297031] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
BACKGROUND Diagnosing postoperative heparin-induced thrombocytopenia (HIT) in cardiothoracic surgical patients is complicated because of the profound thrombocytopenia that occurs with cardiopulmonary bypass (CPB). CPB predisposes patients to develop a frequent incidence of antibodies directed against platelet factor 4 (PF4)/heparin complexes and HIT. The sensitivity of readily available antibody immunoassays is high, but specificity is quite low. The use of both a clinical probability score and rapid laboratory immunoassay has been shown to increase specificity, which is of particular importance in the CPB setting. Prompt diagnosis is crucial because cessation of heparin and treatment with alternative anticoagulation can reduce the risk of thromboembolic events. METHODS We retrospectively reviewed records from cardiothoracic surgical patients whose serum was tested with both the serotonin release assay (SRA) and the PF4/heparin immunoassay from January 2007 through December 2010. We assigned a high, intermediate, or low clinical "4Ts" probability score that quantifies thrombocytopenia, timing of platelet decrease, and thrombotic complications in each patient. We then compared the clinical score and the PF4/heparin immunoassay against the "gold standard" diagnostic test, the SRA. RESULTS The sensitivity and specificity for PF4/heparin optical density >0.40 were 100% and 26%, respectively. Sensitivity and specificity for the diagnosis of HIT with a combination of PF4/heparin optical density >0.40 and high/intermediate 4Ts score were 100% and 70%, respectively. The negative predictive value was 100% for low 4Ts score. CONCLUSIONS We demonstrated that the use of the 4Ts clinical score combined with the PF4/heparin immunoassay for HIT diagnosis increases the sensitivity and specificity of HIT testing compared with the PF4/heparin immunoassay alone. Furthermore, with an intermediate 4Ts score and positive PF4/heparin antibody test, a confirmatory platelet activation assay such as the SRA is necessary. Physicians treating patients after cardiothoracic surgery should recognize the need for an antibody test and confirmation with a platelet activation assay with even moderate clinical probability of HIT.
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Affiliation(s)
- Linda J Demma
- Department of Anesthesiology, Emory University, Atlanta, GA, USA
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Abstract
The current major problem with HIT is its overdiagnosis. This concept follows from the HIT central paradigm: HIT is caused by a subset of antibodies against platelet factor 4 (PF4)/heparin complexes that have strong platelet-activating properties. Prospective studies show that only a minority of sera containing such antibodies exhibit platelet-activating properties. Ironically, the earliest tests for HIT--platelet activation assays--remain today the most diagnostically useful, particularly the washed platelet assays. But the wider application of PF4-dependent immunoassays, and their much greater sensitivity for the larger subset of non-platelet-activating (and non-HIT-inducing) antibodies, has resulted in HIT overdiagnosis in many centres. Studies of anti-PF4/heparin immunization in diverse clinical situations have provided insights into the factors that influence the HIT immune response. Besides the conundrum of anticoagulant-induced thrombosis (including its potentiation of coumarin-induced microthrombosis), HIT evinces numerous other paradoxes: (i) it is a platelet-activating disorder with venous thrombosis as its predominant clinical manifestation; (ii) 'delayed-onset' (or 'autoimmune') HIT can lead to dramatic worsening of HIT-associated thrombosis despite cessation of heparin; (iii) partial thromboplastin time (PTT) monitoring of direct thrombin inhibitor treatment - and confounding of PTT monitoring by HIT-associated consumptive coagulopathy - infers that the worst subset of HIT patients may fail this therapeutic approach; (iv) the highly sulfated pentasaccharide anticoagulant, fondaparinux, can (rarely) cause HIT yet appears to be an effective treatment for this disorder; and (v) the transience of the HIT immune response means that many patients with previous HIT can safely receive future heparin.
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Affiliation(s)
- T E Warkentin
- Department of Pathology and Molecular Medicine, Michael G DeGroote School of Medicine, McMaster University, Hamilton, ON, Canada
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Kim SY, Kim HK, Han KS, Kim I, Yoon SS, Park S, Kim BK. Utility of ELISA optical density values and clinical scores for the diagnosis of and thrombosis prediction in heparin-induced thrombocytopenia. Korean J Lab Med 2011; 31:1-8. [PMID: 21239863 PMCID: PMC3111042 DOI: 10.3343/kjlm.2011.31.1.1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Background Heparin-induced thrombocytopenia (HIT) is an adverse drug reaction caused by antibodies to the heparin/platelet factor 4 (PF4) complex, resulting in thrombocytopenia and prothrombotic state. HIT diagnosis is challenging and depends on clinical presentation and laboratory tests. We investigated the usefulness of clinical scores and heparin/PF4 ELISA optical density (OD) as a diagnostic marker and thrombosis predictor in HIT. Methods We analyzed 92 patients with suspected HIT. The heparin/PF4 antibody was measured using a commercial ELISA kit (GTI, USA). For each patient, the 4 T's score and Chong's score were calculated. Results Of the 92 patients, 28 were anti-heparin/PF4-seropositive. The 4 T's score and Chong's score showed good correlation (r=0.874). The 4 T's score and OD values showed good performance for diagnosis of the definite and unlikely HIT groups; however, OD levels showed better sensitivity (93.8%) than the 4 T's score used alone (62.5%). Of the 92 patients, 26 developed thrombosis. The OD values were significantly higher in patients with thrombosis than in those without thrombosis (0.52 vs. 0.22, P<0.001). Patients with high OD values (OD>0.4) had an increased risk of thrombosis (adjusted odds ratio 9.44 [3.35-26.6], P<0.001) and a shorter 250-day thrombosis-free survival (32.1% vs. 54.7%, P=0.012). Conclusions ELISA OD values in combination with clinical scoring can improve the diagnosis of and thrombosis prediction in HIT. More attention should be paid to the use of clinical scores and OD values as thrombosis predictors in HIT.
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Affiliation(s)
- Seon Young Kim
- Department of Laboratory Medicine, Seoul National University College of Medicine, Seoul, Korea
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Abstract
Heparin-induced thrombocytopenia (HIT) is an antibody-mediated prothrombotic disorder triggered by PF4-binding polyanions, usually heparin. The pentasaccharide anticoagulant, fondaparinux, despite its negative charge and structural similarity to heparin, does not usually promote antibody binding to PF4 (owing to absent/weak 'cross-reactivity'). Thus, despite its ability to trigger anti-PF4/heparin antibodies ('immunogenicity'), fondaparinux has low - but not zero - risk of inducing HIT de novo, or of exacerbating HIT when antibodies are already present. Indeed, despite rare reports of fondaparinux-induced HIT, this 'dissociation' between immunogenicity and cross-reactivity suggests that fondaparinux should be effective in treating HIT, as supported by several observational studies. An emerging issue: will clinicians accept this favorable experience of fondaparinux for treating HIT when a lack of randomized trials will hinder regulatory approval for this indication?
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Affiliation(s)
- Theodore E Warkentin
- Michael G DeGroote School of Medicine, McMaster University, Hamilton, Ontario, Canada.
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Demma LJ, Levy JH. Diagnosing Heparin-Induced Thrombocytopenia in Cardiac Surgical Patients. Anesth Analg 2011; 112:747-9. [DOI: 10.1213/ane.0b013e31820fcc5d] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Bakchoul T, Giptner A, Bein G, Santoso S, Sachs UJH. Performance characteristics of two commercially available IgG-specific immunoassays in the assessment of heparin-induced thrombocytopenia (HIT). Thromb Res 2011; 127:345-8. [PMID: 21232785 DOI: 10.1016/j.thromres.2010.12.001] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2010] [Revised: 12/02/2010] [Accepted: 12/04/2010] [Indexed: 01/12/2023]
Abstract
BACKGROUND The in vitro demonstration of antibodies against platelet factor-4/heparin (PF4/hep) complexes is an important contribution to the diagnosis of heparin-induced thrombocytopenia (HIT). The use of PF4/hep IgG-specific immunoassays enhances the specificity of HIT-investigations without any impairment of the sensitivity. Several IgG-specific immunoassays with different origin and structure of the target antigen-complex are commercially available. METHODS Using a retrospective cohort consisting of 459 patients suspected to have HIT, we compared the performance characteristics of two commercially available IgG-specific immunoassays, GTI- (Genetic Testing Institute) and HIA-IgG-ELISA (Hyphen Biomed Research). RESULTS PF4/hep antibodies were detected in 85 and 81 sera using GTI- and HIA-IgG-ELISA, respectively. OD values and clinical likelihood of patients who tested positive in one assay only were significantly lower than in those who tested positive in both immunoassays. Both IgG-specific assays showed high negative predictive values (100%) and similar but unsatisfactory positive predictive values, determined by a minimum clinical score of 5 and a positive HIPA result (41% and 43%, respectively). The implementation of a confirmatory step using excessive heparin increased the PPV of both assays, but results in a reduction of NPV in HIA-IgG-ELISA. CONCLUSIONS The detection of IgG antibodies alone improves the clinical usefulness of immunoassays. However, functional assays remain indispensable to avoid the overdiagnosis of HIT caused by the detection of IgG non-platelet activating antibodies. The OD value in IgG immunoassays appears to correlate with the clinical relevance of the antibodies and might be used as a predictive parameter in the assessment of HIT.
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Affiliation(s)
- Tamam Bakchoul
- Institute for Clinical Immunology and Transfusion Medicine, Justus Liebig University Giessen, Germany
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83
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Kolde HJ, Dostatni R, Mauracher S. Rapid and simple IgG specific test for the exclusion of heparin induced thrombocytopenia (HIT). ACTA ACUST UNITED AC 2011; 49:2065-8. [DOI: 10.1515/cclm.2011.693] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2011] [Indexed: 11/15/2022]
Abstract
AbstractThe exclusion of heparin induced thrombocytopenia (HIT) is required for selecting the most appropriate anticoagulation therapy in affected patients. It requires the combination of clinical data with the detection of antibodies directed against platelet factor 4 (PF4) in complex with polyanions (PA) such as heparin.We developed a lateral flow immunoassay (LFIA) for PF4/PA complex specific IgG antibodies based on gold nanoparticles. Unlike most other assays, the initial immune reaction takes place in the liquid phase. The sensitivity of the assay has been adjusted with clinical samples aiming in the reliable detection of sera which are positive in a functional platelet activation assay.Sera from 60 patients with suspected HIT were investigated. LFIA identified correctly all samples (n=20) which were positive in a functional assay (HIPA) and an IgG specific ELISA. It correlated with ELISA, but false positive results were less frequent (7 samples were negative with LFIA and HIPA but positive with ELISA).The LFIA may be a suitable tool for the rapid exclusion of HIT within 10 min.
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84
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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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Pendleton RC, Rodgers GM, Hull RD. Established Venous Thromboembolism Therapies: Heparin, Low Molecular Weight Heparins, and Vitamin K Antagonists, with a Discussion of Heparin-Induced Thrombocytopenia. Clin Chest Med 2010; 31:691-706. [DOI: 10.1016/j.ccm.2010.07.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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MOREL-KOPP MC, ABOUD M, TAN CW, KULATHILAKE C, WARD C. Heparin-induced thrombocytopenia: evaluation of IgG and IgGAM ELISA assays. Int J Lab Hematol 2010; 33:245-50. [DOI: 10.1111/j.1751-553x.2010.01276.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Hursting MJ, Pai PJ, McCracken JE, Hwang F, Suvarna S, Lokhnygina Y, Bandarenko N, Arepally GM. Platelet factor 4/heparin antibodies in blood bank donors. Am J Clin Pathol 2010; 134:774-80. [PMID: 20959660 PMCID: PMC3766530 DOI: 10.1309/ajcpg0mnr5ngknfx] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Platelet factor 4 (PF4)/heparin antibody, typically associated with heparin therapy, is reported in some heparin-naive people. Seroprevalence in the general population, however, remains unclear. We prospectively evaluated PF4/heparin antibody in approximately 4,000 blood bank donors using a commercial enzyme-linked immunosorbent assay for initial and then repeated (confirmatory) testing. Antibody was detected initially in 249 (6.6%; 95% confidence interval [CI], 5.8%-7.4%) of 3,795 donors and repeatedly in 163 (4.3%; 95% CI, 3.7%-5.0%) of 3,789 evaluable donors. "Unconfirmed" positives were mostly (93%) low positives (optical density [OD] = 0.40-0.59). Of 163 repeatedly positive samples, 116 (71.2%) were low positives, and 124 (76.1%) exhibited heparin-dependent binding. Predominant isotypes of intermediate to high seropositive samples (OD >0.6) were IgG (20/39 [51%]), IgM (9/39 [23%]), and indeterminate (10/39 [26%]). The marked background seroprevalence of PF4/heparin antibody (4.3%-6.6%) with the preponderance of low (and frequently nonreproducible) positives in blood donors suggests the need for further assay calibration, categorization of antibody level, and studies evaluating clinical relevance of "naturally occurring" PF4/heparin antibodies.
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Affiliation(s)
- Marcie J Hursting
- Duke University Health System, Box 3486, Room 304 Sands Bldg, Durham, NC 27710, USA
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Schindewolf M, Scheuermann J, Kroll H, Garbaraviciene J, Hecking C, Marzi I, Wolter M, Kaufmann R, Boehncke WH, Lindhoff-Last E, Ludwig RJ. Low allergenic potential with fondaparinux: results of a prospective investigation. Mayo Clin Proc 2010; 85:913-9. [PMID: 20843983 PMCID: PMC2947963 DOI: 10.4065/mcp.2010.0346] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
OBJECTIVE To determine the incidence and causes of skin reactions to the synthetic pentasaccharide fondaparinux. PATIENTS AND METHODS Patients who received prophylactic/therapeutic subcutaneous fondaparinux treatment for more than 7 days were prospectively examined for cutaneous adverse effects between September 1, 2008, and April 30, 2009. When indicated, other procedures, such as skin biopsy, allergy testing, and clinical/laboratory assessment for thrombosis and heparin-induced thrombocytopenia, were performed. RESULTS Overall, 231 patients were enrolled. No patient developed typical delayed type IV hypersensitivity (DTH) erythematous skin lesions. However, one female patient experienced abdominal pruritus at sites of injection. Histology revealed a mild lymphohistiocytic infiltrate, confirming a DTH reaction. Heparin-induced thrombocytopenia, as another possible underlying pathomechanism for cutaneous lesions, was ruled out clinically and serologically. Hence, the overall incidence of fondaparinux-induced allergic skin lesions was 0.4% (95% confidence interval, 0.01%-2.4%). No cross-allergies were observed in patients with DTH reaction to heparins. CONCLUSION Fondaparinux has a low allergenic potential. The incidence of allergic cutaneous DTH reactions is almost 20 times lower compared to that with commonly used heparins. These results, together with the known low prevalence of secondary thrombotic events or heparin-induced thrombocytopenia during fondaparinux therapy, suggest that in selected patients fondaparinux might substantially improve patient care, therapeutic safety, and cost-effectiveness of anticoagulant therapy. TRIAL REGISTRATION clinicaltrials.gov identifier: NCT00510432.
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Affiliation(s)
- Marc Schindewolf
- Department of Internal Medicine, J. W. Goethe University Hospital, Theodor-Stern-Kai 7, Bldg. 13A, 60590 Frankfurt am Main, Germany.
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Otis SA, Zehnder JL. Heparin-induced thrombocytopenia: current status and diagnostic challenges. Am J Hematol 2010; 85:700-6. [PMID: 20665476 DOI: 10.1002/ajh.21770] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Heparin-induced thrombocytopenia (HIT) is a fairly common and potentially catastrophic complication of heparin therapy. Diagnosing HIT remains a challenge, as the patients at risk often have other reasons for thrombocytopenia and/or thrombosis. HIT is considered a clinicopathologic disorder whose diagnosis is generally made on the basis of both clinical criteria and the presence of "HIT antibodies" in the patient's serum or plasma. There are two basic laboratory approaches to detect HIT antibodies. The immunoassays detect antibodies based on their binding properties, whereas the functional assays detect antibodies based on their platelet-activating properties. Prompt and accurate diagnosis of HIT is imperative, as overdiagnosis exposes patients to alternative anticoagulants and their associated bleeding risks, whereas under- or delayed diagnosis leaves patients vulnerable to the thromboembolic sequelae of HIT, which can be life threatening. A critical interpretation of laboratory results by the clinician is an essential component of diagnosing HIT. This requires a keen understanding of the current concepts in the pathophysiologic mechanisms of the disease, and the application of these concepts when interpreting the results of both the functional and immunoassays. Equally important is an awareness of the strengths and weaknesses, as well as the current lack of standardization and proficiency testing, of these assays.
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Affiliation(s)
- Stavroula A Otis
- Department of Medicine, Division of Hematology, Stanford University School of Medicine, Internal Medicine (Hematology), 875 Blake Wilbur Drive, Stanford, California, USA.
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Godier A, Flaujac C, Horellou MH, De Mesmay M, Bécanne X, Parisot M, Gauzit R, Samama CM. Argatroban and renal replacement therapy in a morbidly obese patient with heparin-induced thrombocytopenia: A case report. Thromb Res 2010; 126:e141-3. [DOI: 10.1016/j.thromres.2009.12.018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2009] [Revised: 12/22/2009] [Accepted: 12/30/2009] [Indexed: 10/19/2022]
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Abstract
Heparin-induced thrombocytopenia (HIT) is an immune-mediated hypercoagulable disorder caused by antibodies to platelet factor 4 (PF4) and heparin. HIT develops in temporal association with heparin therapy and manifests either as an unexplained thrombocytopenia or thrombocytopenia complicated by thrombosis. The propensity for thrombosis distinguishes HIT from other common drug-induced thrombocytopenias. Diagnosing HIT in hospitalized patients is often challenging because of the frequency of heparin use, occurrence of thrombocytopenia from other causes, and development of asymptomatic PF4/heparin antibodies in patients treated with heparin. This review summarizes our current understanding of the pathogenesis, clinical features, diagnostic criteria, and management approaches in HIT.
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Affiliation(s)
- Gowthami M Arepally
- Division of Hematology, Duke University Medical Center, Durham, North Carolina 27710, USA.
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Current awareness: Pharmacoepidemiology and drug safety. Pharmacoepidemiol Drug Saf 2010. [DOI: 10.1002/pds.1847] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Morel-Kopp MC, Aboud M, Tan CW, Kulathilake C, Ward C. Whole blood impedance aggregometry detects heparin-induced thrombocytopenia antibodies. Thromb Res 2010; 125:e234-9. [PMID: 20053425 DOI: 10.1016/j.thromres.2009.12.001] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2009] [Revised: 10/30/2009] [Accepted: 12/01/2009] [Indexed: 12/28/2022]
Abstract
Heparin-induced thrombocytopenia (HIT) is a serious complication of heparin use. IgG antibodies to complexes of platelet factor 4 (PF4) and heparin trigger the clinical manifestations of HIT. Only a subset of these antibodies will activate platelets and these can only be identified with platelet aggregation (functional) assays. Heparin-induced platelet aggregation (HIPA) and (14)C-serotonin release (SRA) assays for HIT are time-consuming and complex to perform. We have developed a whole blood impedance (WBI) test using the new Multiplate analyser. All samples referred to our laboratory over a 10 month period were screened for heparin-PF4 antibodies by an ELISA method (Zymutest HIA IgG). The 4T's score was used to assess HIT pretest probability. Twenty antibody positive samples were further tested by all three functional assays: light transmission aggregometry (LTA), SRA and WBI. Thirteen out of twenty samples were positive by LTA (10 patients) and 15 by WBI (11 patients). SRA, considered to be the gold standard, was used as a confirmatory test and 11 were found to be positive (10 patients); four discrepant samples were weakly positive by WBI. The prevalence of a positive functional test was strongly correlated with the 4T's clinical risk score, but a small number of low-risk patients had positive functional assays. In this study, the WBI assay detected all SRA positive patients and was positive for two others suggesting greater sensitivity. The rapid and easy to perform assay may be a useful tool for haematology laboratories to detect platelet-activating HIT antibodies.
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Affiliation(s)
- Marie-Christine Morel-Kopp
- Department of Haematology and Transfusion Medicine, Royal North Shore Hospital, Northern Blood Research Centre, University of Sydney, St Leonards, NSW, Australia
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Elalamy I, Galea V, Hatmi M, Gerotziafas GT. Heparin-induced multiple electrode aggregometry: a potential tool for improvement of heparin-induced thrombocytopenia diagnosis. J Thromb Haemost 2009; 7:1932-4. [PMID: 20015320 DOI: 10.1111/j.1538-7836.2009.03600.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Affiliation(s)
- T E Warkentin
- Department of Pathology and Molecular Medicine, Michael G. DeGroote School of Medicine, McMaster University, Hamilton, ON, Canada.
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ASH evidence-based guidelines: is the IgG-specific anti-PF4/heparin ELISA superior to the polyspecific ELISA in the laboratory diagnosis of HIT? Hematology 2009:250-2. [DOI: 10.1182/asheducation-2009.1.250] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Abstract
You are asked to consult on a 76-year-old man admitted to the hospital with pneumonia and thrombocytopenia. Ten days before the current admission, he had undergone surgery to repair a small bowel obstruction. A preoperative platelet count had been normal. Following surgery, he received subcutaneous unfractionated heparin thromboprophylaxis until his discharge on post-operative day 5. In your differential diagnosis for the patient’s thrombocytopenia, you consider heparin-induced thrombocytopenia (HIT) and wish to order laboratory testing. In addition to a polyspecific anti-PF4/heparin ELISA for the diagnosis of HIT, your laboratory has recently begun to offer an IgG-specific ELISA. You wonder which of these assays performs better in the diagnosis of HIT.
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