Rapid determination of anti-heparin/platelet factor 4 antibody titers in the diagnosis of heparin-induced thrombocytopenia

PURPOSE: Heparin-induced thrombocytopenia is mediated by antibodies directed against the heparin-platelet factor 4 (heparin/PF4) complex. Our aim was to investigate whether rapid measurement of anti-heparin/PF4 antibodies could improve the diagnostic workup of patients with suspected heparin-induced thrombocytopenia. METHODS: We examined 148 consecutive patients in our laboratory between January 1995 and June 2001 for suspected heparin-induced thrombocytopenia. Clinical data allowed retrospective assessment of the likelihood of heparin-induced thrombocytopenia. Antibodies against the heparin/PF4 complex were detected by a rapid particle gel immunoassay. RESULTS: Anti-heparin/PF4 antibodies were detected in 69 (47%) of the 148 patients, at dilution titers from 1 to 256. Clinically "likely" or "very likely" heparin-induced thrombocytopenia was significantly more common in patients with titers >or=4 (95% [39/41]) than in those with undetectable antibodies (13% [9/70]; P <0.0001), a titer of 1 (18% [4/22]; P <0.0001), or a titer of 2 (33% [2/6]; P = 0.001). All 19 samples with a positive platelet aggregation test had anti-heparin/PF4 antibody titers of at least 4, including 15 samples with titers >or=32. Thromboembolic complications in heparin-treated patients were significantly more prevalent in patients with titers >or=4 (63% [26/41]) than in those with undetectable antibodies (8% [6/79]; P <0.0001) or a titer of 1 (9% [2/22]; P <0.0001). Of the 11 patients with a titer of 1 who were maintained on heparin, none developed worse thrombocytopenia or thromboembolic complications. CONCLUSION: Anti-heparin/PF4 antibody titers, which can be measured rapidly and reproducibly using a particle gel immunoassay, can be used as a confirmatory test to complement a clinical likelihood score among patients with suspected heparin-induced thrombocytopenia.     

Effect of aspirin on heparin-induced thrombocytopenia (HIT) in a patient requiring hemodialysis

Summary The present report describes the management of a 75-year-old uremic patient with delayedonset heparin-induced thrombocytopenia and clot formation in extracorporeal circulation. The test for serum heparin-dependent platelet aggregation factor was positive and the serum platelet binding IgG (PBIgG) became elevated after the onset of heparin-induced thrombocytopenia. He required continuous exposure to heparin for hemodialysis. One gram of aspirin daily was begun to prevent clot formation in the circuit. Hemodialysis with full heparinization was achieved with no clot formation in the circuit. After aspirin ingestion, the increased level of patient's PBIgG in the presence of heparin and thrombocytopenia were restored to normal. Inhibition of platelet aggregation with aspirin allowed uneventful dialysis in a patient with heparin-induced thrombocytopenia.     

The clinical diagnosis of heparin-induced thrombocytopenia in patients receiving continuous renal replacement therapy

Background Thrombocytopenia is common in critically ill patients who receive continuous renal replacement therapy. Often, these patients receive heparin therapy and the diagnosis of heparin induced thrombocytopenia (HIT) is considered as a potential etiology. No data regarding the clinical diagnosis of HIT is available for patients receiving continuous renal replacement therapy. Patients and methods We performed a retrospective study of 29 consecutive patients who received CRRT in a medical-surgical intensive care unit (ICU) and determined trends in platelet counts following CRRT and the frequency of meeting platelet based clinical criteria for consideration of a HIT diagnosis. Results For patient exposures to CRRT concurrent with heparin, 54% met at least one clinical threshold for consideration of the diagnosis of HIT. In 31% of exposures, both a platelet count <100,000/mm³ and a >50% decrease from baseline were seen. In contrast, the majority (73–85%) of patients receiving CRRT had a low pre-test probability of HIT using the “4T’s” scoring system. Mean platelet counts while on CRRT concurrent with heparin were significantly lower than when patients received heparin alone (P < 0.02). Conclusions The clinical diagnosis of HIT in ICU patients initiating CRRT is challenging given the decrease in platelet counts seen following CRRT initiation in the majority of patients. A prospective study in this population is needed to optimize patient outcomes.     

Heparin-induced thrombocytopenia

Summary Thrombocytopenia is a frequent and sometimes insidious complication of anticoagulant therapy with heparin. Two types of heparin-induced thrombocytopenia with a distinct aetiology have been recognized. Type I is characterized by a mild thrombocytopenia of early onset which requires careful monitoring but usually not the cessation of heparin therapy. The mild thrombocytopenia is probably due to the mild pro-aggregatory properties of heparin and can be more severe in the presence of other predisposing factors, e.g. sepsis. Type II heparin-induced thrombocytopenia is more severe and usually occurs after a period of 7–10 days. Heparin therapy should be ceased immediately and other anticoagulant therapy initiated. The thrombocytopenia is believed to be due to the development of a heparin-dependent antibody that causes platelet aggregation and release. The precise mechanism of heparin-dependent antibody-platelet interaction is still not entirely clear but probably involves the binding of an antibody-heparin immune complex to the platelet Fc receptor.     

Malaria-induced thrombocytopenia

Summary Platelet counts were investigated in 26 patients withP. falciparum malaria and 39 patients withP. vivax malaria before and after treatment. Before schizontocidal treatment 22 of 26 (85%) patients withP. falciparum malaria and 30 of 39 (72%) patients withP. vivax malaria had depressed platelet counts below 150,000/l blood. There was a correlation between low platelet counts and high counts of malarial plasmodia (parasitized red blood cells) inP. falciparum andP. vivax infections (p < 0.001). Platelet survival, studied by malonaldehyde formation in three patients during the period of decreasing parasitaemia, revealed a shortened life span to 2–3 days in comparison to 7–10 days in normal controls. In all patients platelet counts rose to threefold the initial values within 5 days after clearance of parasites.The results demonstrate that, first, thrombocytopenia is a common feature in human malaria, second, thrombocytopenia induced by malaria is due to shortened life span in the peripheral blood and, third, some interaction is present between platelets and malaria plasmodia or parasitized red cells.This study was supported by the Deutsche Forschungsgemeinschaft     

Vaccine-induced immune thrombotic thrombocytopenia

Vaccine-induced immune thrombotic thrombocytopenia (VITT) is primarily a complication of adenoviral vector-based covid-19 vaccination. In VITT, thrombocytopenia and thrombosis mediated by anti-platelet factor 4 (PF4) antibodies can be severe, often characterized by thrombosis at unusual sites such as the cerebral venous sinus and splanchnic circulation. Like in heparin-induced thrombocytopenia (HIT) and spontaneous HIT, VITT antibodies recognize PF4-polyanion complexes and activate PF4-treated platelets but additionally bind to un-complexed PF4, a critical finding that could be leveraged for more specific detection of VITT. Intravenous immunoglobulin and non-heparin-based anticoagulation remain the mainstay of treatment. Second dose/boosters of mRNA covid-19 vaccines appear safe in patients with adenoviral vector-associated VITT. Emerging data is consistent with the possibility that ultra-rare cases of VITT may be seen in the setting of mRNA and virus-like particle (VLP) technology-based vaccinations and until more data is available, it is prudent to consider VITT in the differential diagnosis of all post-vaccine thrombosis and thrombocytopenia reactions.     

Generation of platelet-derived microparticles and procoagulant activity by heparin-induced thrombocytopenia IgG/serum and other IgG platelet agonists: a comparison with standard platelet agonists

Heparin-induced thrombocytopenia (HIT) is a relatively common, immunoglobulin-mediated adverse drug reaction associated with in vivo thrombin generation and both venous and arterial thrombosis. Serum and purified IgG from patients with HIT induce normal platelets to generate procoagulant platelet-derived microparticles, but the magnitude of this response in comparison with other IgG and standard platelet agonists is unknown. We describe a comparison of IgG platelet agonists, including HIT-IgG/serum, heat-aggregated IgG, and platelet-activating murine monoclonal antibodies, with standard 'strong' and 'weak' platelet agonists, and have determined their relative ability to generate platelet procoagulant activity. Using washed normal platelets as targets, we observed that HIT sera as well as other IgG agonists produced similar or even greater numbers of microparticles and procoagulant activity than the standard strong platelet agonists (thrombin, collagen, and thrombin receptor agonist peptide). The only exception was the non-physiological platelet agonist, calcium ionophore, which consistently produced a platelet procoagulant response even greater than the IgG agonists. We conclude that the IgG class of platelet agonists (including pathogenic HIT antibodies) is an effective trigger of the platelet procoagulant response comparable at least to strong physiological platelet agonists. These results help to explain the association between HIT, in vivo thrombin generation, and thrombosis.     

Rapid-onset heparin-induced thrombocytopenia without previous heparin exposure

Heparin-induced thrombocytopenia (HIT) is one of the most common immune-mediated drug reactions. Immunoglobulin G-type antibodies against platelet factor 4(PF4)/heparin complexes are known to play a key role in the pathogenesis of HIT. Rapid-onset HIT is caused by the presence of circulating HIT antibodies at the time of heparin readministration. These antibodies are generally resulted from a recent immunizing exposure to heparin. Here we report a case of rapid-onset HIT developed after a septicemia without previous heparin exposure. The diagnosis of HIT as well as the presence of platelet activating and heparin-dependent antibodies was confirmed by ELISA and flow cytometric functional assays. Our case report reinforces that rapid-onset HIT cannot be excluded only based on the absence of previous heparin exposure. In addition, it may support the new theory of pre-immunization by PF4-coated bacteria in the pathomechanism of HIT. We also call the attention that venous limb gangrene can be rarely associated with HIT and thrombosis even in the absence of coumarin therapy. Furthermore, transient presence of anti-phospholipid antibodies can cause a differential diagnostic problem in the cases of HIT.     

Pentosan polysulfate-induced thrombocytopenia: a case diagnosed with an ELISA test used for heparin-induced thrombocytopenia

 We report a patient who developed severe thrombocytopenia and ischemic stroke following pentosan polysulfate treatment. An ELISA test employed in type-II heparin-induced thrombocytopenia was highly positive. To our knowledge, this is the first case in which this test has been performed in a pentosan polysulfate-induced thrombocytopenia (PIT). Our data suggest that the antibody against pentosan polysulfate-platelet complex also cross-reacts with heparin-platelet factor 4 complex. Due to its greater sensitivity and wider availability, this ELISA test should be used in cases where PIT is suspected. Received: 30 January 1996 / Accepted: 22 April 1996     

替罗非班致极重度血小板减少症一例

1 病例资料 患者男性,68岁.因"发作性胸闷痛10 d"于2012年6月14日16∶24入院.患者10 d前开始静息时反复发作胸闷痛,向肩背部及左上肢放散,伴出汗、乏力,持续10 min至1h不等,每天发作2～3次.既往高血压病史2年.查体:血压140/80 mmHg.意识清,双肺底可闻及少量湿啰音.心界向左侧扩大,心率58次/min,律齐,各瓣膜听诊区未闻及杂音.腹软,肝脾肋下未触及.双下肢无水肿.心电图示窦性心律,Ⅲ、aVF、V7-9导联可见Q波.胸部X线片示左下肺纹理增多模糊,心影外形大.血常规正常,凝血功能正常,肌钙蛋白Ⅰ 12.59μg/L,脑钠肽前体651.88 ng/L,血糖5.8 mmol/L,三酰甘油1.78 mmol/L,低密度脂蛋白胆固醇3.9 nmol/L.     

Haemodialysis-related-heparin-induced thrombocytopenia: Case series and literature review

Heparin-induced thrombocytopenia (HIT) is a serious and life-threatening complication that occurs in five per cent of patients exposed to heparin. It should be considered in patients with a platelet count <100 × 10⁹ cells/l or a >50% decrease from baseline count in association with heparin therapy. Thromboembolic complications develop in 50% of patients. Bleeding is rare as the platelet count nadir typically does not drop below 20 × 10⁹ cells/l. Up to 12% of dialysis patients develop HIT, named haemodialysis-related-heparin-induced thrombocytopenia (HD-HIT), as they are a risk group with continuous exposure to heparin. The definition of HD-HIT is less strict, in the range of a platelet count decrease of 30% and below 150 × 10⁹ cells/l due to the intermittent use of heparin.Heparin cessation and alternative anticoagulation are the key interventions in patients with HIT. In dialysis patients, citrate anticoagulation, heparin-free dialysis or peritoneal dialysis are options that must be considered.The authors describe the presentation, diagnosis, treatment and outcomes of five cases of HD-HIT, and emphasize the importance of an accurate diagnosis and early intervention in order to reduce the mortality risk, which can be as high as 20 per cent.     

主动脉内球囊反搏患者P-选择素与血小板减少症的相关性研究

通过观察主动脉内球囊反搏(IABP)置入前后血浆P-选择素的变化规律,探讨P-选择素与IABP相关血小板减少症发生与发展的关系。方法:选择安贞医院首次放置IABP辅助治疗患者40例。分别于其放置IABP前,放置IABP后12 h、24 h、48 h和72 h,抽取肘正中静脉血样,用酶联免疫吸附实验(ELISA)方法测定血浆P-选择素的浓度。分析IABP放置72 h内血浆P-选择素浓度的变化趋势。根据围手术期期间IABP放置时段的不同,将样本分为3组,分别为术前放置组、术中放置组及术后放置组,分析不同时点放置IABP对血小板活化的影响。结果:对40例患者进行的临床试验研究显示,IABP放置前后血浆P-选择素浓度的差异有统计学意义(P<0.05)。患者血浆中P-选择素的浓度在IABP放置后即开始升高,并于放置后48 h达到峰值,其后开始逐步下降。术前放置IABP、术中放置IABP和术后放置IABP,组间血浆P-选择素的浓度的差异无统计学意义(P>0.05)。结论:IABP置入后血浆P-选择素浓度表达升高,血小板活化程度增强,血小板破坏消耗增多,导致血小板计数减少。     

抗血小板抗体在系统性红斑狼疮血小板减少患者中临床意义的研究

目的 明确抗血小板抗体在系统性红斑狼疮(SLE)血小板减少患者中的临床意义.方法 采用改良抗原捕获酶联免疫吸附试验(ELISA)法检测抗血小板抗体(抗GPⅡb/Ⅲa、GPⅠb/Ⅸ、GPⅠa/Ⅱa、GPⅣ抗体),分别比较治疗前SLE血小板减少与SLE非血小板减少患者抗血小板抗体的阳性率、SLE血小板减少患者治疗前后抗血小板抗体的阳性率、SLE血小板减少治疗前患者病情与抗血小板抗体的关联性.统计方法采用秩和检验和x2检验.结果 治疗前SLE血小板减少组抗GPⅡb/Ⅲa抗体、抗GP Ⅰb,Ⅸ抗体阳性率分别为50%、67%.非血小板减少组阳性率分别为11%、28%,2组间阳性率差异有统计学意义(P＜0.05);治疗后SLE血小板减少组抗GPⅡb/Ⅲa抗体、抗GP Ⅰb/Ⅸ抗体阳性率分别为6%、28%,较治疗前显著降低(P＜0.05);SLE血小板减少组治疗前抗GPⅡb/Ⅲa抗体、抗GP Ⅰb/Ⅸ抗体之间显著关联,该2种抗体均与SLEDAI评分有显著关联性,与抗核抗体、抗双链DNA(dsDNA)抗体、抗中性粒细胞胞质抗体(ANCA)则无显著关联;各组间未检测出抗GPⅣ和GPⅠa/Ⅱa抗体.结论 抗GPⅡb/Ⅲa、GPⅠb/Ⅸ抗体在病情活动SLE血小板减少患者中表达显著升高,与SLE血小板减少病情发生发展和转归相关.

Abstract：

Objective To evaluate the clinical significance of antiplatelet antibody in patients with systemic lupus erythematosus complicated with thrombocytopenia.Methods Antiplatelet antibody (anti-GP Ⅱb/Ⅲa antibody, anti-GP Ⅰb/Ⅸ antibody, anti-GP Ⅰa/Ⅱ a antibody, anti-GP Ⅳ antibody) were detected by modified antigen capture ELISA. The positive rate of antiplatelet antibody between SLE complicated with thrombocytopenia group and without thrombocytopenia group before therapy were compared,and the positive rate of antiplatelet antibody before therapy and after therapy in SLE complicated with thrombocytopenia were compared,and the relevance between antiplatelet antibody and conditions in SLE complicated with thrombocytopenia were analyzed. Rank test and Chi square test were used for statistical analysis. Results The positive rate of anti-GP Ⅱb/Ⅲa antibody and anti-GP Ⅰb/Ⅸ antibody in SLE complicated with thrombocytopenia group before therapy was 50% and 67% respectively, however,the positive rate in SLE without thrombocytopenia group before therapy was 11% and 28% respectively,there was significant difference between the two groups (P＜0.05) and the positive rate of anti-GP Ⅱb/Ⅲa antibody and anti-GP Ⅰb/Ⅸ antibody in SLE complicated with thrombocytopenia group after therapy was 6% and 28% respectively, which was significantly lower than those before therapy (P＜0.05). In SLE complicated with thrombocytopenia group before therapy, there was significant relevance between anti-GP Ⅱb/Ⅲ a antibody and anti-GP[b/Ⅸ antibody, and there was significant relevance between these two antibodies and SLEDAI score,but no significant relevance between these two antibodies and ANA,dsDNA, ANCA. Neither anti-GPⅣ antibody nor anti-GP Ⅰ a/Ⅱ a antibody was detected in patients of this study. Conclusion The positive rate of antiplatelet antibody (anti-GP Ⅱb/Ⅲ a antibody, anti-GP Ⅰb/Ⅸ antibody) is significantly higher in patients with active systemic lupus erythematosus complicated with thrombocytopenia,and these two antibodies are significantly associated with clinical outcomes.     

Whole blood laboratory model of thrombocytopenia for use in evaluation of hemostatic interventions

This study describes a laboratory model of whole blood (WB) thrombocytopenia established with blood from healthy volunteers. We obtained a mean platelet count of 16 × 10⁹/l (95% confidence interval, 10–22) in WB by repeatedly replacing the platelet-rich supernatant with autologous platelet-poor plasma from the same individual. Thrombelastographic profiles of WB clot formation and WB clot stability were performed in parallel with measurements of WB platelet aggregation response. Thrombocytopenia reduced the maximum rate of WB clot formation, while ex vivo addition of platelets reversed the coagulopathy of thrombocytopenia. Control experiments revealed minimal changes in coagulation factors, distribution of bloods cells, and platelet activation capabilities. The WB model appears useful in research, development, and evaluation of the effects of hemostatic interventions in thrombocytopenia.     

Heparin-induced thrombocytopenia in renal insufficiency undergoing dialysis and percutaneous coronary intervention after acute myocardial infarction: A case report

BACKGROUNDHeparin-induced thrombocytopenia (HIT) is a rare complication of heparin therapy, and is characterized by arteriovenous thrombosis and bleeding events. The incidence of HIT after percutaneous coronary intervention (PCI) in patients with myocardial infarction complicated with renal failure is rarely reported.CASE SUMMARYWe report a 73-year-old man with acute myocardial infarction and renal failure who underwent hemodialysis and PCI, and developed a progressive decline in platelets and subcutaneous hemorrhage of both upper limbs after heparin treatment. In addition to a gradual decrease in platelets, the patient’s 4T''s score was 7, and HIT antibody was positive, confirming the diagnosis of HIT.CONCLUSIONPatients receiving heparin combined with antiplatelet therapy should be monitored closely, especially for their platelet count. In the case of thrombo-cytopenia, HIT should be highly suspected. When the diagnosis of HIT is confirmed, timely individualized treatment should be delivered.     

Platelet Satellitism: A Rare,Interesting, In Vitro Phenomenon

Platelet satellitism is a unique, uncommon, in vitro phenomenon seen in peripheral blood smears prepared from EDTA-mixed blood. This is seen in the form of platelets adhering to polymorphonuclear leucocytes imparting a rosette-like appearance. There is no definite causal association with any disease. The cause may be immunological or non-immunological. Severe rosetting may lead to a misdiagnosis of thrombocytopenia unless peripheral smears are examined. Here, we describe a case of incidentally detected platelet satellitism in a healthy 48-year old male subject during a routine check-up.     

Heparin-associated thrombocytopenia: Successful therapy with the heparinoid Org 10172 in a patient showing cross-reaction to LMW heparins

Summary A patient suffering from heparin-associated thrombocytopenia (HAT), recurrent arteriothromboses, and acute renal failure after treatment with standard heparin is described. He failed to improve when therapy was continued with low-molecular-weight (LMW) heparin (Fragmin, Kabi Pfrimmer, Erlangen, FRG). By means of the in vitro heparin-induced platelet activation (HIPA) assay it was shown that standard heparin and the LMW heparins Fragmin and Fraxiparin (Sanofi Labaz, Munich, FRG), as well as the enoxaparine Clexane (Nattermann, Cologne, FRG), all induced platelet activation with the patient's serum. In contrast, the LMW heparinoid Org 10172 (Organon, Oss, The Netherlands) did not cause platelet activation. When the patient was subsequently treated by parenteral administration of Org 10172 as anticoagulant over a period of several weeks the number of platelets rapidly increased and the patient almost completely recovered. This case shows that strong in vivo and in vitro cross-reactivity between standard heparin and LMW heparins may occur, but can be avoided by the use of a novel heparinoid, Org 10172. The HIPA assay provides a simple and sensitive laboratory method for the choice of an innocuous heparin or heparinoid for continued parenteral anticoagulation.     

系统性红斑狼疮伴血小板减少症近远期疗效观察及相关因素研究

目的　研究糖皮质激素治疗系统性红斑狼疮 (SLE)伴血小板减少症的近远期疗效 ,分析影响疗效的相关因素。方法　对 1999— 2 0 0 1年确诊为SLE伴中、重度血小板减少 (血小板 <5 0× 10 9 L) 82例患者进行回顾性分析及随访 ,研究糖皮质激素治疗血小板减少症的近远期疗效及与疾病活动性、骨髓增生程度、血小板抗体 (PAIg)及抗心磷脂抗体 (ACLA)水平因素的相关性。 结果　中、大剂量组 (泼尼松 0 5～ 1mg·kg- 1 ·d- 1 )与超大剂量激素组 (泼尼松≥ 2mg·kg- 1 ·d- 1 )其近期 (4～ 8周 )疗效及远期 (12～ 2 4周 )疗效差异均无显著性 (P >0 0 5 )。具有高活动性组的治疗总有效率优于低活动性组 (P <0 0 1)。骨髓增生活跃组治疗总有效率优于增生低下组的有效率 (P <0 0 5 )。血小板抗体阳性组与阴性组治疗的有效率差异无显著性 (P >0 0 5 )。ACLA阳性组与阴性组的治疗总有效率差异无显著性 (P >0 0 5 )。结论　①激素治疗SLE伴中、重度血小板减少症以相当于泼尼松 0 5～ 1mg·kg- 1 ·d- 1 为宜 ,大剂量激素的主要副作用是增加感染 ;②活动性高及骨髓增生度好的患者对治疗的反应好。     

非体外循环冠状动脉旁路移植术中肝素诱导血小板减少并血栓形成一例

1病例资料 患者女性,59岁,因“阵发性心前区闷痛6年,加重1年”,于2012年3月9日入院。既往有高血压、糖尿病病史,一直口服药物治疗,血压、血糖控制可。入院前曾皮下使用肝素抗凝治疗。入院查体：血压140／70mmHg（1mmHg=0．133kPa）,心肺查体未见明显异常。实验室检查,血常规：     

急性甲型肝炎伴血小板减少及溶血性贫血1例报告

急性甲型肝炎是急性感染HAV后导致的以乏力、黄疸、腹部不适、食欲减退、肝功能异常为特征的肝损伤,而免疫介导的肝外表现和血液学并发症在急性甲型肝炎中相对少见,主要见于成人急、慢性乙型肝炎和丙型肝炎[1]。查阅国内外文献发现关于急性甲型肝炎同时并发血小板减少和溶血性贫血非常罕见。本科室近期收治了1例中年男性感染HAV后导致重度血小板减少和溶血性贫血的病例,现报告如下。