Heparin-Induced Thrombocytopenia (HIT) Testing at ARUP Laboratories. Heparin-induced thrombocytopenia (HIT) is a complication of heparin therapy. HIT is characterized by a 30-50% decrease in platelet count and an increased thrombotic risk due to platelet activation. Without treatment, up to 50% of patients can experience thrombotic events ID-PaGIA Heparin/PF4 Antibody Test (Kit) Description: Rapid test for the exclusion of heparin induced thrombocytopenia (HIT). (Id-n°: 45580) Configuration: Reagent 1: Red polystyrene particles coated with human platelet factor 4 and heparin. Reagent 2: Gel card with anti-human-IgG. Negative and positive controls. Principl
Introduction Heparin-induced thrombocytopenia (HIT) is an acute, immune-mediated process that may result in life-threatening thrombosis. HIT is caused by platelet-activating, heparin-dependent antibodies, who form complexes of heparin together with either platelet factor-4 (PF-4) (most of the clinical cases), interleukin-8 (IL-8) or neutrophil-activating peptide 2 (NAP-2) Heparin-induced thrombocytopenia is a complication of treatment with the blood-thinner (anticoagulant) heparin that can cause low platelets in the blood and an increased risk of excessive blood clotting.This test detects and measures antibodies that may be produced by your immune system when or after you are treated with heparin
Diagnosing and treating Heparin Induced Thrombocytopenia (HIT) represent a challenge for many clinicians. STic Expert® HIT is a significant step forward in HIT diagnosis. Patients with HIT have a very high thrombosis risk. They require alternative anticoagulant treatments which increase the bleeding risk. In the absence of a rapid and reliable. Description. HIT CONFIRM - HARNESSING THE POWER OF FLOW CYTOMETRY - Confirmation of Heparin-induced thrombocytopenia (HIT) The Emo-test HIT Confirm® has been developed by Emosis to address the need of clinicians and laboratories to get access to an HIT activity test that would be readily available, on-demand, 24/7, affordable and easy to use by non-specialists The ID-PaGIA Heparin/PF4 Antibody Test Kit is a rapid, gel agglutination assay for antibodies directed against the complex of platelet factor 4 (PF4) and heparin. It is a very simple and economical procedure used for the exclusion of heparin-induced thrombocytopenia (HIT), with results available in less than 20 minutes heparin-induced thrombocytopenia. N.Engl.J Med. 2001;344:1286-1292. 8. Amiral J, Bridey F, Wolf M et al. Antibodies to macromolecular platelet factor 4-heparin complexes in heparin-induced thrombocytopenia: a study of 44 cases. Thromb Haemost. 1995;73:21-28. 9. Kelton JG, Sheridan D, Santos A et al. Heparin PF4 ELISA Results in the Clinical. From Ginger Weeden, MLS (ASCP)cm, Bio-Rad Laboratories: George, What heparin-induced thrombocytopenia with thrombosis (HIT) testing is available in the US?I'm wondering how many manufacturers there are. Thanks for any information. Hi, Ginger, and thanks for your question. All the C14 serotonin release assay methods (washed platelets) available from reference labs are laboratory-developed tests
Here is the link for Hyphen BioMed's HIT kits. Hyphen BioMed's HIT IgG was the first kit 510K cleared by FDA. www.hit-assay.com. ZYMUTEST HIA kits offer a range of immuno-assays designed for testing heparin dependent antibodies, involved in the development of Heparin Induced Thrombocytopenia (HIT) or Heparin Induced Thrombocytopenia and Thrombosis (HITT) The American Society of Hematology (ASH) recommends the 4Ts clinical scoring system, which is widely used to assess pretest probability for heparin-induced thrombocytopenia (HIT). This system takes into account the severity and timing of thrombocytopenia, the presence of thrombosis or other complication(s), and the likelihood of another cause of thrombocytopenia Antibody related to heparin-induced thrombocytopenia. Easy-to-interpret results window, 1 package insert and 6 individual sealed pouches, each pouch contains 1 PIFA™ heparin/PF4 minireactor device. Heparin/PF4 Rapid Assay Kit. This item has been discontinued by the manufacturer and is no longer available This ELISA assay detects the presence of IgG antibodies to heparin-platelet factor 4 (PF4) complexes. Most cases of heparin-induced thrombocytopenia (HIT) are caused by IgG antibodies to heparin-PF4, rather than IgA or IgM antibodies. Negative results have a good negative predictive value for HIT, although rare false-negative results may occur HIPA results should not be the sole basis for establishing the diagnosis of heparin-induced thrombocytopenia. Some patients with HIPA will not develop symptoms of heparin-induced thrombocytopenia (HIT). Microbial contamination, lipemia, icterus, or hemolysis may interfere with this test and immune complexes or immunoglobulin aggregates in the.
Clinical features. The thrombocytopenia of HIT is typically of moderate severity, with median platelet counts ranging between 50-80×10 9 /l. 18 It may be absolute (that is, <150×10 9 /) or relative (that is, a drop of 50% or more) compared with the pre‐heparin value, although the nadir may remain >150×10 9 /l. Severe thrombocytopenia (platelets <15×10 9 /l) is unusual 2. Principles of Functional Assays. In functional tests, donor platelets are incubated with patient serum/plasma and heparin. If clinically significant patient′s HIT antibodies are present with an optimal heparin-PF4 stoichiometric ratio, this leads to the formation of a heparin-antibody-PF4 complex that will bind to FcγRIIa receptors on the platelet and induce donor platelets activation HIT — Heparin- Induced Thrombocytopenia test ( 20) Catalog Number. MQHIT 1. Short Info. Lateral Flow Assay designed for the detection of IgG antibodies against PF4 / polyanion- complexes in human citrated plasma or Serum. This product is only available in Germany! Method/ Patform. lateral flow, immunoassay Heparin-induced thrombocytopenia (HIT) is a distinct immune-mediated state in which laboratory detection of the antibodies is extremely useful. This functional flow cytometric assay assesses the ability of a test sample to activate platelets in the presence of heparin. HITAlert™ Kit Features. Functional assessment of platelet activation where.
. Negative results have a good negative predictive value for HIT, although rare false-negative results may occur. Positive ELISA results are sensitive but not completely specific for HIT Heparin-induced thrombocytopenia is a complication of treatment with the blood-thinner (anticoagulant) heparin that can cause low platelets in the blood and an increased risk of excessive blood clotting. This test detects and measures antibodies that may be produced by your immune system when or after you are treated with heparin
LIFECODESPF4 Family Products. LIFECODES PF4 Enhanced and PF4 IgG have been designed to detect antibodies that have been implicated in causing Heparin Induced Thrombocytopenia (HIT). LIFECODES PF4 is offered in multiple kit formats allowing the flexibility to detect either IgG/A/M or IgG specific antibodies. 1,2 Chromogenix Coatest® Heparin is a chromogenic assay kit for the in vtiro diagnostic photometric determination of heparin in human plasma. The Coatest® Heparin test kit determines the anti-FXa activity of LMW heparin and UF heparin. Excellent reagent stability. Suitable for both large and small laboratories Heparin-induced thrombocytopenia (HIT) is an adverse drug reaction caused by heparin. HIT occurs due to IgG antibodies directed against heparin-bound platelet factor 4 (PF4). The aim of this study was to evaluate the STic® Expert HIT for detection of anti-PF4/heparin antibodies in comparison with ID-PaGIA™ kit. The results were further confirmed by Heparin-induced platelet aggregation test. Heparin-induced thrombocytopenia (HIT) Immune complexes (heparin-PF4-IgG) cause platelet activation via the platelet Fcγreceptor for IgG (FcγRIIA) Thrombocytopenia High risk of thrombosis Occurs in ~50% of untreated cases May be venous (DVT, PE) or arterial (limb ischemia, stroke, MI) Thrombotic complications can be fata
The Heparin Dependent Antibody test should be ordered only in patients with a 4T Score at or above this level. Useful for the qualitative detection in serum of the anti-heparin platelet factor (PF4) antibodies generated during the type II heparin induced thrombocytopenia (HIT type II) by ELISA. There are two types of heparin-induced. Heparin-induced thrombocytopenia Type II (HIT) is an acute, immune-mediated process that may result in life-threatening thrombosis. 1 HIT is caused by heparin-dependent antibodies formed to complexes of heparin/platelet factor-4 (HPF-4). 2,3 These antibodies are initially formed when a patient has been on heparin therapy for 5 or more days. An immune response to a heparin dose may be observed.
In clinical practice, immunoassays are pivotal for the workup of patients with suspected heparin-induced thrombocytopenia (HIT). 1-4 HIT is a life-threatening complication of heparin therapy that affects a significant number of patients. 5 It is associated with a high morbidity and mortality because of a massive pro-coagulant state, with a high incidence of extensive venous and arterial. . They named the modified assay the PF4-induced platelet activation test (PIPA) Test Kit is intended for use as a qualitative procedure for the detection of anti‐heparin‐platelet factor 4 (anti-Heparin-PF4) heparin‐induced thrombocytopenia (Type II HIT), a condition that occurs during heparin therapy, leading to arterial or venous thrombosis. Assay Type ; Qualitative Fetal Cell Count kit HITAlert (Heparin Induced Thrombocytopenia) Antibodies test Single Double Triple CD4-FITC CD4+CD19 CD4+CD8+CD3 Heparin-induced thrombocytopenia (HIT) is an acute, immune-mediated process that may result in life-threatening thrombosis
For every Heparin Induced Thrombocytopenia (HIT) suspicion. A rapid and specific exclusion of Heparin Induced Thrombocytopenia in 10 minutes. Diagnosing and treating Heparin Induced Thrombocytopenia (HIT) represent a challenge for many clinicians. STic Expert® HIT is a significant step forward in HIT diagnosis Diagnosis of Heparin-Induced Thrombocytopenia Karen A. Moser, MD Heparin-induced thrombocytopenia (HIT) is a complication seen in approximately 1%-3% of patients treated with unfractionated heparin therapy. HIT may also be associated with low molecular weight heparin use.1 Clinical symptoms include moderate thrombocytopenia and Greinacher A, Ittermann T, Bagemuhl, et al. Heparin-induced thrombocytopenia: towards standardization of platelet factor 4/heparin antigen tests. J Thromb Haemost 2010;8:2025- 31. Sheridan D, Carter C, Kelton JG. A diagnostic test for heparin-induced thrombocytopenia. Blood 1986;67:27-30. Sono-Koree NK, Crist RA, Frank EL, et al A third type of drug-induced thrombocytopenia (heparin-induced thrombocytopenia or HITP) occurs in patients treated with heparin to prevent or treat thrombosis. Heparin is a family of polysaccharide species consisting of chains made up of alternating, 1-4 linked and variously sulfated residues of glucuronic acid or iduronic acid and D-glucosamine The anti-PF4 (ie, heparin-induced platelet antibody) test is an immunologic, enzyme-linked immunosorbent assay (ELISA) that detects IgG antibodies against the platelet factor 4 (PF4)/heparin complex. The assay uses heparin bound to protamine sulfate, and PF4 is supplemented through a platelet lysate
Heparin-induced thrombocytopenia (HIT) is a drug-induced thrombocytopenia that results in thrombotic complications rather than bleeding.In many countries like India, the availability of functional assay for diagnosing HIT is unavailable. - HIT antibody testing was done using ID-PaGIA Heparin/pF4 Antibody Test Kit with control. In this 10. The flow cytometry-based HIT Confirm® test is a first-in-class functional test with results available in 30 minutes, 24/7, on-site and on-demand. It is the first test that could contribute, even in emergency situations, to the diagnosis of the potentially lethal and rather frequent Heparin-Induced Thrombocytopenia (HIT) suspicion i HIT is a major issue in ICU because: heparin (UFH) or LMWH is nearly universal in ICU patients. thrombocytopenia is common (up to 50%) complications of HIT can be severe. Two types. HIT type I, a benign non-immune condition. HIT type II, an immune-mediated syndrome caused by an antibody to the PF4/heparin complex — what we mean when we say. Theodore E. Warkentin, William E. Dager, in Chemistry and Biology of Heparin and Heparan Sulfate, 2005 B Heparin-Induced Thrombocytopenia Antibody-Induced Platelet Activation. Only anti-PF4/heparin antibodies of IgG class have the potential to activate platelets (22, 23).This is because platelet activation occurs when the platelet FcγIIa receptors are occupied by IgG antibodies that recognize.
This rare but serious clotting complication may occur after receiving the Johnson & Johnson or Oxford-AstraZeneca COVID-19 vaccines. This phenomenon, called vaccine-induced immune thrombotic thrombocytopenia, appears to present clinically and pathologically similarly to heparin-induced thrombocytopenia (HIT) Cautions. Heparin-induced thrombocytopenia (HIT) is a clinical diagnosis that is complemented by laboratory testing for heparin-dependent platelet aggregation (HDPA) antibodies and/or antibodies to human platelet factor 4 (H/PF4) complexes. Assay results provide information on the presence or absence of H/PF4 antibodies, which are implicated in. ABSTRACT: Heparin-induced thrombocytopenia (HIT) is a potentially. life-threatening reaction to heparin that occurs in approximately 0.2% to 5% of patients and has an estimated mortality rate of 20%. The core management goal of HIT is to stop administration of heparin from all sources and initiate an alternative nonheparin anticoagulant
Heparin-induced thrombocytopenia (HIT) is the development of thrombocytopenia (a low platelet count), due to the administration of various forms of heparin, an anticoagulant.HIT predisposes to thrombosis (the abnormal formation of blood clots inside a blood vessel) because platelets release microparticles that activate thrombin, thereby leading to thrombosis Haemostasis specialist, Stago, has launched a new assay to rapidly exclude heparin-induced thrombocytopenia (HIT) in as little as10 minutes. Based on lateral flow technology, the STic Expert HIT kit provides a quick and easy way of ruling out HIT, allowing clinicians to make faster, better-informed decisions for improved patient care
Warkentin, T. E. Clinical picture of heparin-induced thrombocytopenia (HIT) and its differentiation from non-HIT thrombocytopenia. Thromb. Haemost. 116 , 813-822 (2016) The HITAlert Kit™ is a CE/IVD functional assay for the diagnosis of Heparin Induced Thrombocytopenia. This kit uses donor platelets (PRP) which are incubated in the presence of patient serum and in the presence or absence of heparin. A platelet activation marker is used to identify and quantitate the activated platelets caused by pathogenic antibodies, which can be visualised using flow. Rapid Test Kits. Materials and Reagents. Adjuvant; Serum-Free Cell Freezing Medium; Antibody Isotyping Kits platelet factor 4; heparin-platelet factor-4; HPF-4; HIT; heparin-induced thrombocytopenia; heparin-associated thrombocytopenia; HAT; HIT-I; Heparin-PF4. Human Heparin-PF4 complex/HIT IgM ELISA Kit (DEIABL73) Size: 96T. Species.
Heparin induced thrombocytopenia (HIT) and thrombosis are serious side effects of heparin therapy caused by antibodies that recognize complexes consisting of heparin and platelet factor four (PF4). Current ELISA methods which test for HIT antibodies are non-specific and have a high false positive rate 1. Greinacher A et al, Heparin-associated thrombocytopenia: isolation of the antibody and characterization of a molecular PF4-heparin complex as the major antigen. Thromb. Haemost. 1994, 71(2) 247-251 1. 2. Warkentin TE et al, Heparin-induced thrombocytopenia in patients treated with low-molecular-weight-heparin or unfractionated heparin Heparin-induced Thrombocytopenia. It is a possible side effect of a blood thinner medication, heparin, which is used to cure blood clots. Blood clots are formed due to an immune reaction to the drug. All you need to do is order a test kit from Lab Me, perform it at home and mail it back 150031 Synonyms Vaccine-Associated Coagulopathy; Vaccine-Induced Immune Thrombotic Thrombocytopenia; VITT Antibody Test HLA DRB3,4,5 High Resolution 167357 Special Instructions For assistance, please email HLACS@labcorp.com or call 1-800-533-1037
A diagnosis of heparin induced thrombocytopenia (HIT) must often be made based on clinical and laboratory evidence. This was a quasi-experimental study of patients admitted from June 2016 to October 2017. The primary endpoint was the incidence of false positive results in polyspecific and IgG specific enzyme-linked immunosorbent assay (ELISA); then we compared the sensitivity and specificity. screening test for heparin-induced thrombocytopenia (HIT) could be used as a reliable replacement for ELISA methodology (the Asserachrom HPIA kit, Bayer Healthcare). The potential advantages of the ID-PaGIA method over the ELISA technology are that it is simple to perform, the test can be completed i Testkits > Heparin Induced Thrombocytopenia (HIT) Description. Enzyme immuno-assay designed for specifically measuring heparin-dependent antibodies of IgG, or IgM, or IgA isotype, in human plasma or serum, or in any biological fluid where these antibodies must be measured. Specific isotyping assay Heparin Induced Thrombocytopenia (HIT) Heparin QC Kits ; Latex Assays (CE Marked 15min Covid-19 Nasal Swab) x 20 Test Kit. GCCOV-502a. View Product. Accu-Tell SARS-CoV-2 Ag Rapid Test Cassette (CE Marked 10min COVID-19 Nasal Swab) x 20 Test Kit. ABT-IDT-B367
The occurrence of aggressive thrombosis and thrombocytopenia in SARS-CoV-2-vaccinated patients suggested similarities between VITT and HITT and led investigators to test patients for the presence of antibodies to PF4-heparin complexes. Antibodies to complexes of heparin or heparinlike polyanions (used in commercial enzyme-linked immunosorbent. Background: Heparin‐induced thrombocytopenia (HIT) is a prothrombotic immune‐mediated adverse drug reaction. Antigen and platelet activation assays are used for detection of antibodies. Quantitative results from platelet factor 4 (PF4)‐dependent immunoassays may lead to inter‐laboratory standardization of measurements. Objectives: The aim was to modify a PF4‐dependent immunoassay to. Introduction. Heparin-induced thrombocytopenia (HIT) is a prothrombotic and potentially fatal complication of heparin treatment caused by anti-platelet factor 4 (anti-PF4)/heparin antibodies of immunoglobulin G (IgG) class, affecting approximately 0.1% to 5% of patients receiving unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH). As heparin is widely administered in clinical. Versiti releases new test for detecting blood clots after vaccine. Versiti, Inc., a blood health and research organization, unveiled a comprehensive diagnostic testing menu for suspected vaccine-induced immune thrombotic-thrombocytopenia (VITT) in the United States. Cases of patients developing clots (thrombosis) with low platelet counts.
The present study aimed to explore the clinical characteristics of heparin-induced thrombocytopenia (HIT) after surgery for acute type A aortic dissection and perform a relevant prognostic analysis. After continuous observation and analysis of 204 patients who underwent acute type A aortic dissection, we found that blood platelets decreased significantly after surgery and that these patients. PEI/Bfarm listed COVID Antigen Test Kit Antigen Nasal Swab/Saliva Rapid Test Kit(5 tests packing) Read More. This also inactivates heparin-induced thrombocytopenia IgG antibodies. The antibody test cannot measure the immunity of Covid. But this is how they can help you Use of other drugs inducing thrombocytopenia Has the patient received other drugs inducing thrombocytopenia? 1 YES 2 NO 1. Antibiotic therapy:. Heparin remains widely used. However, it is associated with a serious complication, heparin-induced thrombocytopenia (HIT). Heparin-induced thrombocytopenia is an immune-mediated process secondary to the formation of antibodies that recognize platelet factor 4-heparin (PF4/heparin) complexes. 1 -8 This leads to platelet activation and is associated with a very strong risk of thrombotic events The assay is not quantitative and is reported as either positive or negative based on whether the colour intensity exceeds a kit-specific cut-off value. Clinical details: Approximately 5% of patients on unfractionated heparin therapy develop type 2 heparin-induced thrombocytopenia (HIT)
Heparin-induced thrombocytopenia (HIT) is an iatro- the score is ≥4 points,we would test an antiplatelet factor 4-heparin antibody (HIT antibody) before surgery,and anti-PF4/H antibody detection kit shows that the corre-sponding value is no less than a threshold of 1.5 OD or U/mL (the same below).. Type 2 heparin-induced thrombocytopenia (referred to herein as HIT), is a drug-induced, immunoglobulin-mediated thrombocytopenic disorder that is often associated with severe venous or arterial thrombosis attributed to the formation of platelet thrombi (Cines, D. B., et al., N. Engl J Med, 31:581 (1987); Celoria, G. M., et al., Angiology, 39. Heparin-induced thrombocytopenia (HIT) is an immune-mediated syndrome of thrombocytopenia and thrombosis as a result of heparin exposure. HIT is the most common type of drug-induced, immune-mediated thrombocytopenia and is associated with high morbidity and mortality if undiagnosed.. The wide use of heparin in hospitalised patients demonstrates that HIT can develop in patients receiving the. The present invention relates to a flow cytometry assay for the determination of heparin-induced thrombocytopenia. This method (a) detects in a plasma sample the presence of anti-heparin antibodies which react with platelets in the presence of heparin to produce activated platelets, (b) quantitates by flow cytometry the presence of such activated platelets in the plasma sample, and (c. Aniara Diagnostica provides you with a comprehensive offering of diagnostic and research agents, as well as screening tools, all designed to meet today's highest standards in terms of product quality. You can also rely on Aniara for cost-effective delivery and around-the-clock customer service
Heparin induced thrombocytopenia (HIT) is a life-threatening disorder which diagnosis depends on laboratory evaluation. The objective of this report is to present the impact of different laboratory methods for HIT detection on the diagnostic evaluation process Incidence of Antiheparin−Platelet Factor 4 Antibodies and Heparin-Induced Thrombocytopenia in Turkish Patients Undergoing Cardiac Surgery. Clinical and Applied Thrombosis-hemostasis, 2007. Muzaffer Turgut. Download PDF. Download Full PDF Package. This paper. A short summary of this paper The diagnosis of heparin-induced thrombocytopenia (HIT) may be affirmed by demonstrating heparin-dependent anti-platelet antibodies using the 14C-serotonin release assay (SRA). In this study, results of the SRA was compared with the recently described platelet factor 4 (PF4)/heparin enzyme-linked immunosorbent assay (ELISA) difference in the heparin induced antibody positivity between - the two heparin preparations, UFH and LMWH (p-value 0.463) and between the different patient categories (p-value 0.214). Conclusion This study shows that Heparin induced thrombocytopenia (HIT) syndrome is rare in KNH
Introduction. Heparin-induced thrombocytopenia (HIT) is an adverse drug reaction caused by antibodies to the heparin/platelet factor 4 (PF4) complexes. HIT diagnosis is challenging and depends on clinical presentation and laboratory tests. We investigated the interest of the combined use of 4 Ts score and the functional and immunological tests. Rauova, L. et al. Monocyte-bound PF4 in the pathogenesis of heparin-induced thrombocytopenia. Blood 116 , 5021-5031 (2010). CAS Article Google Schola The 4Ts clinical scoring system can be combined with the particle gel assay for heparin antibody to strengthen the post-test probability of HITT his constitutes an efficient strategy for application in suspected HIT patients to assist timely management including discontinuing all types of heparin and substituting an alternative anticoagulant8 Activation of platelets by heparin-induced thrombocytopenia antibodies in the serotonin release assay is not dependent on the presence of heparin. J Thromb Haemost 3: 2168-2175, 2005. Crossref | PubMed | ISI Google Scholar; 35. Rauova L , Zhai L , Kowalska A , Arepally GM , Cines DB , Poncz M
Abstract: Prompt diagnostic work-up of suspected heparin-induced thrombocytopenia (HIT) is critical for guiding initial patient management. We assessed the performance of three immunoassays detecting anti-PF4/heparin-antibodies, derived a diagnostic algorithm with a short analytical turnaround-time (TAT) and prospectively validated it Summary Introduction Heparin‐induced thrombocytopenia (HIT) is an immune‐mediated complication of heparin therapy. Our objective was (i) to compare various laboratory assays for HIT against clinical probability (4‐T score) and 14C‐serotonin release assay (SRA), which was the composite gold standard and (ii) to determine the incidence of HIT in the ICU. Methods The study group (n = 217.
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 Clinical features of heparin-induced thrombocytopenia including risk factors for thrombosis: a retrospective analysis of 408 patients. Thromb. Haemost. 94,132-135 (2005). Preachel, M. & Walenga, J. The laboratory diagnosis and clinical management of patients with heparin-induced thrombocytopenia: an update The purpose of this research is to identify genomic markers that can predict heparin-induced thrombocytopenia (HIT), which is a very serious side effect to heparin. Heparin is commonly used to prevent blood clots and the investigators may be able to identify genomic markers which can be used to prevent heparin use in people who will get HIT