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.

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.

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.

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

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.

Frequency and Clinical Impact of Platelet Factor 4-Specific Antibodies in Patients Undergoing Extracorporeal Membrane Oxygenation

2019 ◽  
Vol 119 (07) ◽  
pp. 1138-1146 ◽  
Author(s):  
Caroline Vayne ◽  
Marc-Antoine May ◽  
Thierry Bourguignon ◽  
Eric Lemoine ◽  
Eve-Anne Guery ◽  
...  
Keyword(s):  
Platelet Count ◽  
Extracorporeal Membrane Oxygenation ◽  
Serotonin Release ◽  
Clinical Impact ◽  
Platelet Factor 4 ◽  
Ecmo Circuit ◽  
Platelet Factor ◽  
Specific Antibodies ◽  
Release Assay ◽  
Specific Igg

Introduction/Objectives Extracorporeal membrane oxygenation (ECMO) provides circulatory support in patients with severe heart failure, but the frequent use of unfractionated heparin exposes patients to high risk of heparin-induced thrombocytopenia (HIT). We prospectively evaluated the development and clinical impact of platelet factor 4 (PF4)-specific antibodies (Abs) during ECMO and whether specific biological characteristics could predict HIT. Materials and Methods From 2014 to 2018, we studied 57 adults who underwent an ECMO for at least 5 days. The plasma samples collected daily were tested for PF4-specific Abs using immunoassays to detect immunoglobulin (Ig) G, A, and M isotypes or only IgG. Serotonin release assay was performed without and with PF4 to detect pathogenic Abs. Results Twenty-nine patients (50%) were positive for PF4-specific Abs (IgG, A, M), with IgG in 17/57 (30%) and 16 of them (94%) were immunized within 10 days. PF4-specific IgG Abs did not affect the clinical or biological course of most patients. HIT was suspected in only two patients with ECMO circuit dysfunction and unexpected platelet count decrease after day 5. High levels of PF4-specific IgG were detected in both patients, and HIT was confirmed by a serotonin release assay, which was also more sensitive when exogenous PF4 was present. Conclusion PF4-specific Abs are common during ECMO but are mostly non-pathogenic and not associated with a less favorable prognosis. However, an abnormal platelet count evolution, in particular if associated with ECMO circuit dysfunction, should prompt the search for pathogenic PF4-specific IgG.

Antibodies to the Platelet Factor 4-Heparin Complex and Mortality in Chronic Hemodialysis Patients.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 274-274
Author(s):  
Marc Carrier ◽  
Greg A. Knoll ◽  
Dean Fergusson ◽  
Steven Doucette ◽  
Michael J. Kovacs ◽  
...  
Keyword(s):  
Cardiovascular Events ◽  
Hemodialysis Patients ◽  
Serotonin Release ◽  
Chronic Hemodialysis ◽  
Platelet Factor 4 ◽  
Elisa Assay ◽  
Platelet Factor ◽  
Risk Of Death ◽  
Asymptomatic Patients ◽  
Release Assay

Abstract Background: Heparin-induced thrombocytopenia is a serious complication of heparin therapy that can lead to thromboembolism, cardiovascular events or death. Patients with this disorder develop antibodies to the platelet factor 4-heparin (PF4-H) complex. Hemodialysis patients are repeatedly exposed to heparin and are at risk for developing PF4-H antibodies. The clinical impact of asymptomatic PF4-H antibodies in patients on chronic hemodialysis is not known. Objective: To determine the association between asymptomatic PF4-H antibodies and mortality in a cohort of chronic hemodialysis patients repeatedly exposed to heparin. Methods: Pre-dialysis blood samples were drawn from 419 asymptomatic patients. All patients received unfractionated heparin (Baxter) while on dialysis. All samples were screened for PF4-H antibodies using an ELISA assay (GTI PF4 Enhanced, GTI Diagnostics). All positive and indeterminate samples were then tested using an IgG-specific PF4-H ELISA assay and a platelet serotonin-release assay. Participants were then followed up prospectively for thromboembolic events, cardiovascular events, or death. Results: During a median follow-up of 2.5 years there were 129 deaths. After controlling for important potential confounding variables, the relative risk of death was 2.92 (95% CI: 1.18-7.25; P= 0.02) in patients with IgG-specific PF4-H antibodies and 4.08 (95% CI: 1.26–13.2; P= 0.02) in patients with IgG-specific antibodies and an indeterminate serotonin-release assay. Conclusions: PF4-H antibody formation is associated with increased all-cause mortality in patients on chronic hemodialysis. Further investigation is needed to determine if anticoagulation with alternative agents would improve survival in this population.

scholarly journals Diagnostic Performance of Heparin-Platelet Factor 4 Antibodies in the Identification of Heparin-Induced Thrombocytopenia in Cancer Population

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 4896-4896
Author(s):  
Thein H. Oo ◽  
Cristhiam Mauricio Rojas Hernandez
Keyword(s):  
Cancer Patients ◽  
Serotonin Release ◽  
Diagnostic Tools ◽  
Cancer Center ◽  
Antibody Testing ◽  
Platelet Factor ◽  
Heparin Induced Thrombocytopenia ◽  
Release Assay ◽  
Md Anderson ◽  
4T Score

Introduction: Cancer patients appear to have a higher risk of heparin induced thrombocytopenia (HIT) related complications than non-cancer patients; yet data on the performance of conventional diagnostic tools for HIT in cancer is limited. Our aim was to determine among cancer patients with a 4T score ≥ 4, the performance of the conventional cut-off for HIT antibody testing (IgG anti PF4) to discriminate between serotonin release assay (SRA) positive and negative cases. Methods: Retrospective and prospective analysis of cases (2002-2019) was performed of the electronic medical records of adult cancer patients at MD Anderson Cancer Center with suspected HIT. Cases were included in the analysis if the 4T score was ≥ 4 and investigated with IgG anti-PF4 optical density (HIT OD) and SRA. Logistic regression model and the receiver operating characteristic curves were conducted to identify the sensitivity and specificity of different cut-off points for the HIT OD to discriminate HIT cases based on the SRA status. Results: Among 50 cases, 18 were SRA positive. Median HIT OD was 1.03. At a cut-off point of 0.4, the HIT OD performed with a sensitivity of 0.89 and a specificity of 0.50 to discriminate the cases of SRA positive HIT. When the cut-off HIT OD was 1.0, the sensitivity was 0.78 with a specificity of 0.66. Conclusions: Our findings suggest that in cancer patients the performance of IgG anti-PF4 is similar to that of non-cancer patients for the identification of HIT cases. Disclosures Oo: Janssen and Janssen: Other: Research: site co-investigator ; Medical Education Speakers Network: Honoraria.

A New Enzyme Immuno-Assay That Only Detects IgG Antibodies to Heparin-PF4 Complexes (Zymutest HIA IgG®) Improves the Specificity of the Diagnosis of HIT without Loss of Sensitivity.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 2096-2096
Author(s):  
Claire Pouplard ◽  
Sandra Regina ◽  
Jean Baptiste Valentin ◽  
Yves Gruel
Keyword(s):  
Platelet Activation ◽  
High Specificity ◽  
Serotonin Release ◽  
Igg Antibodies ◽  
Platelet Factor ◽  
Heparin Induced Thrombocytopenia ◽  
Release Assay ◽  
Immuno Assay ◽  
Enzyme Immuno Assay ◽  
Test Probability

Abstract Heparin-induced thrombocytopenia (HIT) is associated in most patients with the development of antibodies to heparin-modified platelet factor 4 (PF4). Commercial immuno-assays frequently detect these antibodies after cardiac surgery but only few patients develop clinical HIT. Therefore, platelet activation tests such as serotonin release assay (SRA) are necessary to ensure the diagnosis of HIT with high specificity. Another approach to increase diagnosis specificity could be to detect IgG antibodies which are of major clinical relevance since they are the only class able to directly activate platelets in the presence of heparin. Therefore, we evaluated the performances of a new commercial immuno-assay specific to IgG for the diagnosis of HIT Abs (Zymutest HIA IgG®, Hyphen Biomed, Neuville sur Oise, France). Samples from 101 patients with suspected HIT were analysed. 40 cases had developed significant levels of Abs to PF4 measured with PVS/PF4 ELISA (HAT45®,GTI, Brookfiled, WI, USA) and the diagnosis of HIT had been confirmed since SRA was positive. Every sample was then tested with a global assay named Zymutest HIA G/A/M® as followed: each diluted plasma (200 μl) was incubated for 1 hour with 50 μl of platelet lysate providing PF4 into wells previously coated with unfractionated heparin. After washings and incubation (1 hour) with anti IgG/A/M-HRP immunoconjugate, the enzyme activity was developed and absorbance was read at 450nm. In case of positive result (A450 ≥ 0.5), the isotype distribution was analysed with a specific and standardized assay using monospecific anti-IgG-, anti-IgA- and anti IgM-HRP conjugates (Zymutest HIA-IgG® or -IgA® or -IgM®). A450 values ≥ 0.5 were also considered as positive. GTI assay that detected IgG/A/M Abs to PVS/PF4 complexes in the 40 patients with HIT (Ss 100%) was also positive in 30 of the 61 cases with no HIT (Sp 50.8%). Comparatively, Zymutest HIA® global assay was positive in 39 of the 40 patients with HIT (Ss 97.5%) and in 14 of 61 cases without HIT (Sp 77%). On the other hand, significant levels of heparin-dependent IgG antibodies were also measured in these 39 HIT patients using Zymutest HIA IgG® assay (mean A450: 1.81; range A450: 0.5 – 2.76), and only in 6 patients without HIT (Sp: 90%). However, IgG levels measured in patients without HIT were significantly lower (mean A450: 0.60; range A450: 0.08 – 2.20) than in those with HIT (p < 0.0001). In addition, IgA or IgM heparin-dependent antibodies were only present, i.e. without IgG, in samples from patients for whom the diagnosis of HIT had been ruled out (n = 3). In conclusion, this study supports that the detection of significant levels of IgG heparin-dependent antibodies improves the diagnosis specificity in patients with a suspicion of HIT without loss of sensitivity. Nonetheless, whether IgG-specific immunoassays could avoid to perform platelet activation tests in patients with a strong pre-test probability of HIT warrant further study.

Sign in / Sign up

Export Citation Format

Share Document