Prevalence of Heparin-Dependent Platelet Antibodies in Children after Cardiopulmonary Bypass Surgery.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 3019-3019
Author(s):  
Rowena C. Punzalan ◽  
Sheila J. Hanson ◽  
Nancy Ghanayem ◽  
Brian R. Curtis ◽  
Kathleen Murkowski ◽  
...  
Keyword(s):  
Cardiopulmonary Bypass ◽  
Unfractionated Heparin ◽  
Pediatric Intensive Care ◽  
Serotonin Release ◽  
Platelet Factor 4 ◽  
Enzyme Linked Immunosorbent Assay ◽  
Platelet Factor ◽  
Heparin Induced Thrombocytopenia ◽  
Platelet Antibodies ◽  
Release Assay

Abstract Heparin is used during cardiopulmonary bypass (CPB) surgery in children. Upon exposure to heparin, heparin-dependent platelet antibodies (HDPA) may form against complexes of platelet factor 4 and heparin on platelet surfaces. Heparin-induced thrombocytopenia (HIT) or heparin-induced thrombocytopenia and thrombosis (HITT) may then ensue. Among adult CPB patients, up to 50% demonstrate HDPA, although only 2% develop HIT and 1% develop HITT. In previous studies done among non-CPB newborns and pediatric intensive care patients, the incidence of HDPA has been zero to minimal. Objective: To determine prevalence of HDPA among children undergoing CPB who are exposed to unfractionated heparin for >120 hours after CPB. Methods: We designed a prospective pilot study. All patients ≤ 12 years old who were to receive heparin during CPB were eligible. The presence of HDPA was assessed by heparin-platelet factor 4 enzyme-linked immunosorbent assay (ELISA); positive and equivocal results were confirmed by serotonin release assay. Blood samples were obtained at the time of cessation of heparin or after 10 days on heparin, whichever came first. Results: Thirty patients were enrolled: 15 were aged 2–19 days (median 6 days); 15 were aged 1.2 to 50 months (median 4.5 months). One patient had borderline positive and 1 had positive results by heparin-platelet factor 4 ELISA; both had negative results by serotonin release assay; neither developed clots. Eighteen patients developed thrombocytopenia, which is common after CPB, including the 2 with equivocal results by ELISA. Six patients, all with negative ELISAs, developed symptomatic thromboses. Conclusion: There were no HDPA identified among children who received unfractionated heparin for CPB. The specificity of heparin-platelet factor 4 ELISA among children should be assessed.

Pathophysiology of Heparin-Induced Thrombocytopenia

2000 ◽  
Vol 124 (11) ◽  
pp. 1657-1666 ◽  
Author(s):  
Fabrizio Fabris ◽  
Sarfraz Ahmad ◽  
Giuseppe Cella ◽  
Walter P. Jeske ◽  
Jeanine M. Walenga ◽  
...  
Keyword(s):  
Platelet Activation ◽  
Serotonin Release ◽  
Platelet Factor 4 ◽  
Thrombin Inhibitors ◽  
Platelet Factor ◽  
Cellular Activation ◽  
Heparin Induced Thrombocytopenia ◽  
New Information ◽  
Study Selection ◽  
Release Assay

Abstract Objective.—This review of heparin-induced thrombocytopenia (HIT), the most frequent and dangerous side effect of heparin exposure, covers the epidemiology, pathophysiology, clinical presentation, diagnosis, and treatment of this disease syndrome. Data Sources and Study Selection.—Current consensus of opinion is given based on literature reports, as well as new information where available. A comprehensive analysis of the reasons for discrepancies in incidence numbers is given. The currently known mechanism is that HIT is mediated by an antibody to the complex of heparin–platelet factor 4, which binds to the Fc receptor on platelets. New evidence suggests a functional heterogeneity in the anti-heparin-platelet factor 4 antibodies generated to heparin, and a “superactive” heparin-platelet factor 4 antibody that does not require the presence of heparin to promote platelet activation or aggregation has been identified. Up-regulation of cell adhesion molecules and inflammatory markers, as well as preactivation of platelets/endothelial cells/leukocytes, are also considered to be related to the pathophysiology of HIT. Issues related to the specificity of currently available and new laboratory assays that support a clinical diagnosis are addressed in relation to the serotonin-release assay. Past experience with various anticoagulant treatments is reviewed with a focus on the recent successes of thrombin inhibitors and platelet GPIIb/IIIa inhibitors to combat the platelet activation and severe thrombotic episodes associated with HIT. Conclusions.—The pathophysiology of HIT is multifactorial. However, the primary factor in the mediation of the cellular activation is due to the generation of an antibody to the heparin-platelet factor 4 complex. This review is written as a reference for HIT research.

Serologic Results in >1000 Patients With Suspected Heparin-Induced Thrombocytopenia

2007 ◽  
Vol 14 (4) ◽  
pp. 410-414 ◽  
Author(s):  
Suresh G. Shelat ◽  
Anne Tomaski ◽  
Eleanor S. Pollak
Keyword(s):  
Laboratory Diagnosis ◽  
Serotonin Release ◽  
Enzyme Linked Immunosorbent Assay ◽  
Functional Assay ◽  
Platelet Factor ◽  
Heparin Induced Thrombocytopenia ◽  
Life Threatening ◽  
Release Assay ◽  
Pathogenic Antibodies

Heparin-induced thrombocytopenia (HIT) can lead to life-threatening and limb-threatening thrombosis. HIT is thought to be initiated by the interaction of pathogenic antibodies toward a complex platelet factor 4 (PF4) and heparin (PF4:H), which can activate platelets and predispose to thrombosis. As such, the laboratory diagnosis of HIT includes antigenic and functional assays to detect antibodies directed at PF4:H complexes. We performed a retrospective analysis of 1017 consecutive samples tested by serotonin-release assay and by enzyme-linked immunosorbent assay (ELISA). Most samples showed no serologic evidence of HIT, whereas 4% to 5% of samples demonstrated both antigenic and functional serological evidence for HIT. Approximately 12% to 18% of samples showed immunologic evidence of anti-PF4:H antibodies but without functional evidence of serotonin release in vitro. Interestingly, a small minority of samples (0.7%) caused serotonin release but were negative in the ELISA. The results are presented using cutoff values established at our hospital and for the ELISA manufacturer. This study provides a pretest probability of the serologic results from an antigenic assay (ELISA) and a functional assay (serotonin-release assay) in patients clinically suspected of having HIT.

Platelet factor-4 concentration in adult veno-arterial ECMO patients

Perfusion ◽  
2020 ◽  
pp. 026765912096510
Author(s):  
Michael Mazzeffi ◽  
Madeline Clark ◽  
Alison Grazioli ◽  
Colleen Dugan ◽  
Raymond Rector ◽  
...  
Keyword(s):  
Antibody Formation ◽  
Critical Factor ◽  
Epidemiologic Studies ◽  
Serotonin Release ◽  
Platelet Factor 4 ◽  
Platelet Factor ◽  
Heparin Induced Thrombocytopenia ◽  
Release Assay ◽  
Va Ecmo ◽  
Control Plasma

Background: Heparin induced thrombocytopenia (HIT) is reported at a variable rate in extracorporeal membrane oxygenation (ECMO) patients. A critical factor impacting platelet factor-4 (PF4)-heparin antibody formation is plasma PF4 concentration. We hypothesized that PF4 concentration would be increased during veno-arterial (VA) ECMO. Methods: Plasma PF4 concentration was measured during the first 5 ECMO days in 20 VA ECMO patients and 10 control plasma samples. PF4-heparin ratios were estimated using an assumed heparin concentration of 0.4 IU/mL. This correlates with an activated partial thromboplastin time of 60 to 80 seconds, which is the anticoagulation target in our center. Results: Twenty VA ECMO patients were enrolled, 10 of which had pulmonary embolism. Median PF4 concentration was 0.03 µg/mL [0.01, 0.13] in control plasma. Median PF4 concentration was 0.21 µg/mL [0.12, 0.34] on ECMO day 1 or 2, 0.16 µg/mL [0.09, 0.25] on ECMO day 3, and 0.12 µg/mL [0.09, 0.22] on ECMO day 5. Estimated median PF4-heparin ratios were 0.04, 0.03, and 0.02 respectively. Two patients (10%) developed HIT that was confirmed by serotonin release assay. PF4 concentration did not differ significantly in these patients compared to non-HIT patients (p = 0.37). No patient had an estimated PF4-heparin ratio between 0.7 and 1.4, which is the reported optimal range for PF4-heparin antibody formation. Conclusion: Our data suggest that PF4 concentration is mildly elevated during VA ECMO compared to control plasma. Estimated PF4-heparin ratios were not optimal for HIT antibody formation. These data support epidemiologic studies where HIT incidence is low during VA ECMO.

scholarly journals Staged Management of Heparin-Induced Thrombocytopenia for Renal Cavo-Atrial Cancer Removal on Cardiopulmonary Bypass

2021 ◽  
Author(s):  
Salim Aziz ◽  
Shailendra Sharma ◽  
Jenna Aziz ◽  
James Gould ◽  
Xiomara Fernandez
Keyword(s):  
Cardiopulmonary Bypass ◽  
Platelet Reactivity ◽  
Circulatory Arrest ◽  
Serotonin Release ◽  
Successful Outcome ◽  
Enzyme Linked Immunosorbent Assay ◽  
Platelet Activity ◽  
Heparin Induced Thrombocytopenia ◽  
Platelet Receptor ◽  
Release Assay

Management of patients with acute heparin-induced thrombocytopenia (HIT) with cavo-atrial renal cancer requiring surgery on cardiopulmonary bypass (CPB) and possible deep hypothermia circulatory arrest is a challenge. A staged approach using Bivalirudin, plasmapheresis, and intravenous immunoglobulin (IVIG) was used to preoperatively de-escalate HIT guided by enzyme-linked immunosorbent assay (ELISA) and serotonin release assay (SRA). Intraoperatively heparin was used as the anticoagulant for CPB as DHCA was likely to be used to remove the atrio-caval tumor. Heparin is effective in preventing clots in the circuit during DHCA. To prevent HIT upon re-exposure to heparin during CPB, a bolus of a Cangrelor (reversible P2Y12 platelet receptor inhibitor) was given before heparin and during CPB whilst platelet activity was monitored using platelet reactivity units (PRU). Postoperatively, to prevent recurrence of HIT, plasmapheresis was used until SRA and optical density (OD) resulted. The patient had a successful outcome.

scholarly journals Heparin-Induced Thrombocytopenia Testing: ELISA Based Anti-Platelet Factor 4 Polyspecific and IgG-Specific Antibody Detection Assays Compared to the Unfractionated Heparin Serotonin Release Assay

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 3209-3209
Author(s):  
Edward C.C. Wong ◽  
Laura A. Worfolk ◽  
Caixia Bi ◽  
Lina J. Noh ◽  
Andrew Espinoza ◽  
...  
Keyword(s):  
Unfractionated Heparin ◽  
Specific Antibody ◽  
Serotonin Release ◽  
Test Results ◽  
Platelet Factor ◽  
Heparin Induced Thrombocytopenia ◽  
Specific Antibodies ◽  
Functional Assays ◽  
Antibody Assays ◽  
Release Assay

Abstract Introduction: Antibodies that cause heparin-induced thrombocytopenia (HIT) can be detected with either antigenic or functional assays. Previously, it has been shown that antigenic (ELISA based) assays that detect anti-platelet factor 4 (anti-PF4) IgG, IgM, or IgA (polyspecific) antibodies are more sensitive but less specific than functional assays such as the unfractionated serotonin release assay (UFH SRA), and that the use of anti-PF4 assays that detect IgG antibodies only, would increase the specificity but decrease the sensitivity of these assays for the detection of HIT antibodies that are prothrombotic (associated with positive functional assay). To date large epidemiologic studies have not confirm these findings. To evaluate the relative performance of anti-PF4 polyspecific and IgG-specific antibodies in their ability to detect prothrombotic HIT antibodies, we evaluated results of non-reflexive HIT panels that contained either anti-PF4 polyspecific or IgG-specific assays and unfractionated heparin serotonin release assays over an eight-year period at a U.S. reference laboratory. Methods: Test results for 2 HIT detection panels were compared: 1 panel had UFH SRA plus the polyspecific PF4 ENHANCED® assay (GTI Diagnostics, Waukesha, WI) and 1 panel had UFH SRA plus the IgG-specific Zymutest HIA IgG assay (Hyphen Biomed, France). Test results were from the last 4 years of use for each panel (2009 to 2012 for the polyspecific panel; 2017 to 2020 for the IgG-specific panel). UFH SRA was performed as described by Sheridan et al, (1986) with positivity defined as ≥20% serotonin release by low dose UFH and >50% suppression of release at high dose (100 U/mL) UFH. For each year and assay, test results were stratified by optical density (OD) results, and the percent of results positive by UFH SRA was determined for each OD range. Median yearly UFH SRA positivity rates for each OD interval were compared for anti-PF4 polyspecific vs IgG-specific antibody assays using non-parametric statistical testing, Mann-Whitney U test, two-tailed, with significance defined as <0.05. Results: HIT panels with either ELISA based assays detecting either anti-PF4 polyspecific or IgG specific antibodies demonstrated increasing UFH SRA positivity rates as OD increased. Approximately 50% UFH SRA positivity occurred when OD was in the 2.000 to range. No significant differences in SRA positivity were seen at any positive OD interval when comparing anti-PF4 polyspecific vs IgG-specific assays. A small but significant difference was seen when OD results were considered This observation may have been due to a in the review process (2017-2020): when a UFH SRA result was positive with a negative OD result, repeat UFH SRA testing was performed. Conclusions: Our study demonstrates that the correlations of UFH SRA positivity and OD measurements are similar for anti-PF4 IgG-specific and polyspecific antibody assays. These results suggest the assay types may perform similarly for the detection of HIT and importantly provide important predictive information as to when an optical density value will lead to a positive UFH SRA result. Figure 1 Figure 1. Disclosures Wong: Quest Diagnostics: Current Employment, Current equity holder in publicly-traded company, Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company. Worfolk: Quest Diagnostics: Current Employment. Bi: Quest Diagnostics: Current Employment. Noh: Quest Diagnostics: Current Employment. Espinoza: Quest Diagnostics: Current Employment. Wu: Quest Diagnostics: Current Employment. Sahud: Quest Diagnostics: Current Employment. Racke: Quest Diagnostics: Current Employment. Dlott: Quest Diagnostics: Current Employment.

scholarly journals False-Negative Platelet Factor 4 Antibodies and Serotonin Release Assay and the Utility of Repeat Testing in the Diagnosis of Heparin-Induced Thrombocytopenia and Thrombosis

2019 ◽  
Vol 2019 ◽  
pp. 1-4 ◽  
Author(s):  
Tarig Omer ◽  
Naresh Mullaguri ◽  
Pravin George ◽  
Christopher R. Newey
Keyword(s):  
False Negative ◽  
Serotonin Release ◽  
Clinical Suspicion ◽  
Platelet Factor 4 ◽  
Platelet Factor ◽  
Heparin Induced Thrombocytopenia ◽  
Repeat Testing ◽  
Tandem Occlusion ◽  
Release Assay ◽  
The Right

Objective. To report a case of false-negative serological tests in the diagnosis of heparin-induced thrombocytopenia (HIT) followed by a brief review of the literature on this topic. Case Presentation. A 75-year-old Caucasian female patient was admitted with a traumatic right ankle fracture that required open reduction and internal fixation. Despite postoperative subcutaneous heparin chemoprophylaxis, she developed deep vein thrombosis (DVT) and pulmonary embolism (PE) on day 4 and subsequently started on continuous heparin infusion. On day 5, she suffered a stroke from a complete occlusion of the right common carotid artery with tandem occlusion of the right middle cerebral artery. She underwent successful thrombectomy of both arteries. The proposed stroke mechanism was paradoxical embolism through a patent foramen ovale. Over the next few days, thrombocytopenia was noted, the heparin drip was stopped, and HIT antibodies (antibodies targeting the complex of platelet factor 4 and heparin; PF4-H AB) and serotonin release assay (SRA) tests were sent. Because of the suspicion for HIT, she was started on bivalirudin with subsequent improvement in platelet count. Initial PF4-H AB and SRA tests were negative, bivalirudin was stopped, and heparin was restarted. Subsequently, her platelets trended down, again raising clinical suspicion of HIT. Repeat PF4-H AB and SRA testing resulted positive. Conclusions. A positive SRA in the appropriate context is considered for the diagnosis of heparin-induced thrombocytopenia. This case report highlights that false-negative serological evaluation is possible early in the course of the disease. Repeat testing is recommended in patients with high clinical suspicion.

Serotonin‐release assay‐positive but platelet factor 4‐dependent enzyme‐immunoassay negative: HIT or not HIT ?

2020 ◽  
Author(s):  
Theodore E. Warkentin ◽  
Maureen A. Smythe ◽  
Mona A. Ali ◽  
Naveed Aslam ◽  
Jo‐Ann I. Sheppard ◽  
...  
Keyword(s):  
Enzyme Immunoassay ◽  
Serotonin Release ◽  
Platelet Factor 4 ◽  
Platelet Factor ◽  
Release Assay

scholarly journals Clinical Significance of the Serotonin Release Assay and Platelet Count Monitoring After Cardiac Surgery

2017 ◽  
Vol 24 (6) ◽  
pp. 944-949 ◽  
Author(s):  
Shinya Motohashi ◽  
Takefumi Matsuo ◽  
Hidenori Inoue ◽  
Makoto Kaneko ◽  
Shunya Shindo
Keyword(s):  
Cardiac Surgery ◽  
Platelet Count ◽  
Clinical Course ◽  
Serotonin Release ◽  
Enzyme Linked Immunosorbent Assay ◽  
Heparin Induced Thrombocytopenia ◽  
Release Assay ◽  
Immunological Assays ◽  
Platelet Count Monitoring ◽  
The Relationship

Heparin-induced thrombocytopenia (HIT) is one of the serious complications in patients who undergo cardiac surgery. However, there remains a major problem in diagnosing HIT because the current immunological assays for detection of HIT antibody have limitations. Furthermore, the clinical course of thrombocytopenia in this surgery makes it increasingly difficult to diagnose HIT. We investigated the relationship between platelet count and HIT antibody in 59 patients who underwent cardiac surgery using cardiopulmonary bypass (CPB). The number of postoperative HIT antibody-positive patients evaluated using enzyme-linked immunosorbent assay kit (polyanion IgG/IgA/IgM complex antibodies/antiplatelet factor 4 enhanced) was 37 (62.7%). In contrast, platelet activation by HIT antibody was evaluated using the serotonin release assay (SRA). More than 20% and 50% release of serotonin was obtained from 12 patients (20.3%) and 8 patients (13.6%), respectively. The levels of d-dimer were significantly different on postoperative day 14 between SRA-positive and SRA-negative groups; however, postoperative thrombus complication was not detected using sonography in the patients with positive serotonin release at all. After being decreased by the operation, their platelet count recovered within 2 weeks in both groups equally. In our study, although the patients were positive in the platelet activating HIT antibody assay, they remained free from thrombosis and their platelet count recovered after early postoperative platelet decrease. Therefore, in addition to the SRA, monitoring of platelet count might be still considered an indispensable factor to facilitate the prediction of HIT thrombosis prior to manifestation in the patients undergoing cardiac surgery using CPB.

Investigations of the Immunoglobulin Subtype Transformation of Anti–Heparin-Platelet Factor 4 Antibodies During Treatment With a Low-Molecular-Weight Heparin (Clivarin) in Orthopedic Patients

2003 ◽  
Vol 127 (5) ◽  
pp. 584-588
Author(s):  
Sarfraz Ahmad ◽  
H. Peter Bacher ◽  
Michael R. Lassen ◽  
Debra A. Hoppensteadt ◽  
Helen Leitz ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Low Molecular Weight Heparin ◽  
Serotonin Release ◽  
Platelet Factor 4 ◽  
Enzyme Linked Immunosorbent Assay ◽  
Low Molecular Weight ◽  
Platelet Factor ◽  
Significant Difference ◽  
Antibody Titers ◽  
Orthopedic Patients

Abstract Context.—It is now widely accepted that the pathophysiology of heparin-induced thrombocytopenia (HIT) syndrome is mediated by the generation of a wide array of functional and molecularly heterogeneous anti–heparin-platelet factor 4 (AHPF4) antibodies that may mediate platelet and/or endothelial cell activation/destruction. Objective.—We investigated the differential prevalence and functionality of AHPF4 immunoglobulin subtypes (IgA, IgG, and IgM) in plasmas obtained from orthopedic patients immobilized with Plaster-Cast and treated with clivarin (a low-molecular-weight heparin) in comparison to a placebo for the prophylaxis of deep-vein thrombosis. Design and Methods.—Clivarin was administered subcutaneously at a fixed daily dosage of 1750 U without any adjustment or loading dosage. Citrated plasmas were obtained at baseline, at 10 to 14 days, and at postbrace procedure (5–12 weeks). An enzyme-linked immunosorbent assay (ELISA) was used to quantitate the AHPF4 antibody titers. The functionality of the ELISA-positive samples was determined by a 14C-serotonin release assay (SRA). Results.—In the ELISA test, 16 of 1073 samples (1.5%; 6 in clivarin and 10 in placebo groups) were positive for AHPF4 antibodies (mean optical density [OD] = 0.46 ± 0.02). None of the ELISA-positive samples for AHPF4 antibodies could mediate platelet activation responses as determined by the SRA (0%–3% serotonin release, P > .10, n = 16). Through differential immunoglobulin subtype analysis of the samples positive for (cumulative) AHPF4 antibodies, we determined that their relative prevalence in plasma were as follows: IgM (mean OD = 0.71 ± 0.13) > IgG (0.31 ± 0.08) > IgA (0.14 ± 0.02). Although there was no significant difference in the total antibody titers between clivarin and placebo groups, the antibody subtyping data showed conversion trends (ie, IgA [clivarin to placebo], IgG [placebo to clivarin], and IgM [clivarin to placebo]). Conclusion.—These observations indicate that even at reduced dosages, clivarin can shift the immunogenic up-regulation toward the IgG subpopulation; however, the IgG subtype is of a nonfunctional type of AHPF4 antibody and thus may not cause any HIT-related pathogenic responses.

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