Biomedical subjects
Publications and source records attributed to A Greinacher.
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Commercial immunoassays frequently detect anti-PF4/heparin antibodies during mechanical circulatory support (MCS), but only a small minority of patients develops heparin-induced thrombocytopenia (HIT). Whereas platelet functional tests can distinguish between platelet-activating and non-platelet-activating antibodies, commercial PF4-dependent immunoassays do not. Between 2003 and 2004, 113 patients were placed on MCS. Blood samples were obtained on postimplant day 5-7 for analyses by antibody assays and the functional heparin-induced platelet activation (HIPA) assay. Three distinct groups of patient sera were identified: platelet-activating anti-PF4/heparin antibodies (n = 10), non-platelet-activating anti-PF4/heparin antibodies (n = 53), and anti-PF4/heparin antibody negative (n = 50). Patients with platelet-activating antibodies had the highest risk for thromboembolic events (P < 0.005), whereas those with non-platelet-activating antibodies did not differ from antibody negative patients (P = 0.369). The enzyme-immunoassay and column agglutination assays, which cover all immunoglobulin classes, demonstrated adequate sensitivity and negative predictive value; yet, both lacked specificity with respect to the platelet-activating antibodies. If all antibody positive patients were further classified by an IgG-specific anti-PF4/heparin enzyme-immuno assay, specificity for platelet-activating antibodies increased. Whereas IgG-specific optical density (OD) values below 1.0 were likely for non-platelet-activating anti-PF4/heparin antibodies, higher values were progressively predictive for pathogenic platelet activation. The probability of the development of clinical HIT also increased steeply. In conclusion, platelet-activating anti-PF4/heparin antibodies are relatively common (about 9%) in patients on MCS and are associated with significantly higher thrombotic event rates. Low IgG-specific OD values (< 1.0) in the enzyme-immunoassay indicate low likelihood for the presence of platelet-activating antibodies. These results justify further validation so that anticoagulation during MCS becomes safer and adequate.
This report describes fatal disseminated cardiovascular thrombosis associated with Fc-receptor IIa-mediated platelet activation during surgery for aortic valve replacement in a patient with endocarditis. The patient's serum contained antibodies which strongly activated platelets via the Fc-receptor IIa. Antibodies did not bind to platelet factor 4 or aprotinin and binding was independent of heparin. The mechanisms and differential diagnosis for such a complication are discussed. Our data show for the first time in a patient with endocarditis that, beside HIT, other immune complexes can induce massive intravascular coagulation via platelet Fc-receptor IIa activation.
BACKGROUND: Heparin-induced thrombocytopenia (HIT) is a prothrombotic adverse drug reaction caused by heparin. As thrombocytopenia is common in hospitalized patients receiving heparin, it would be useful to have a clinical scoring system that could differentiate patients with HIT from those with other reasons for thrombocytopenia. AIM: To compare prospectively the diagnostic utility of a clinical score for HIT in two different clinical settings. METHODS: The pretest clinical scoring system, the '4 T's', was used to classify 100 consecutive patients referred for possible HIT in one hospital (Hamilton General Hospital, HGH) into high, intermediate, and low probability groups. This system was also used to classify likewise 236 patients by clinicians in Germany referring blood for diagnostic testing for HIT in Greifswald (GW). The clinical scores were correlated with the results of laboratory testing for HIT antibodies using the serologic criteria for HIT with high diagnostic specificity. RESULTS: In both centers, patients with low scores were unlikely to test positive for HIT antibodies [HGH: 1/64 (1.6%), GW: 0/55 (0%)]. Patients with intermediate [HGH: 8/28 (28.6%), GW: 11/139 (7.9%)] or high scores [HGH: 8/8 (100%), GW: 9/42 (21.4%)] were more likely to test positive for clinically significant HIT antibodies. The positive predictive value of an intermediate or high clinical score for clinically significant HIT antibodies was higher at one center (HGH). CONCLUSIONS: A low pretest clinical score for HIT seems to be suitable for ruling out HIT in most situations (high-negative predictive value). The implications of an intermediate or high score vary in different clinical settings.
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Venous thromboembolism is a common complication in critically ill patients, resulting in high morbidity and mortality. Most patients treated in intensive care units (ICU) face a high risk of thromboembolic complications. There is a need for well-defined strategies for prevention of thrombosis in ICU patients. Mechanical methods such as compression stockings are frequently used, even though evidence for these measures in ICU patients is limited. Unfractionated heparin (UFH) is still the leading drug for thromboprophylaxis in ICU patients, but pharmacokinetic disadvantages such as low predictability of effect on anticoagulation are relevant, especially in ICU patients. Additionally, there is no sufficient evidence from clinical trials to support subcutaneous or intravenous prophylaxis with UFH. At least equivalent efficacy and safety of subcutaneous low molecular weight heparin (LMWH) compared with subcutaneous UFH have been shown in numerous studies investigating non-ICU high-risk groups. First studies on the use of LMWH in critically ill patients are promising. Some conclusions for safe use of subcutaneous LMWH in ICU patients can be drawn. Intravenous LMWH may be the optimal prophylaxis in most ICU patients, but there is a lack of sufficient data on dosing. Precautions such as monitoring of anticoagulation in patients with renal insufficiency are fundamental if LMWH is given. Further investigations into prevention of venous thromboembolism in ICU patients are urgently needed.
OBJECTIVES: To assess efficacy and safety of lepirudin in patients with heparin-induced thrombocytopenia (HIT) in a prospective study (HAT-3) as well as in a combined analysis of all HAT study data. PATIENTS/METHODS: Patients with laboratory-confirmed HIT were treated with lepirudin in three different aPTT-adjusted dose regimen and during cardiopulmonary bypass (CPB). Endpoints were new thromboembolic complications (TEC), limb amputations, and death and major bleeding. A historical control group (n = 120) was used for comparison. RESULTS: After start of lepirudin in 205 patients treated in HAT-3, the combined endpoint occurred in 43 (21.0%). Thirty (14.6%) patients died, 10 (4.9%) underwent limb amputation, and 11 (5.4%) new TECs occurred. Major bleeding occurred in 40 patients (19.5%) (seven during CPB surgery). Combining all prospective HAT trials (n = 403), after start of lepirudin treatment, the combined endpoint occurred in 82 patients (20.3%), with 47 deaths (11.7%), 22 limb amputations (5.5%), 30 new TECs (7.4%), and 71 (17.6%) major bleedings. Compared with the historical control group (log-rank test), the combined endpoint after start of treatment was reduced (29.7% vs. 52.1%, P = 0.0473), primarily because of reduction in new thromboses (11.9% vs. 32.1%, P = 0.0008). Mean lepirudin maintenance doses ranged from 0.07 to 0.11 mg kg(-1) h(-1). Major bleeding was more frequent in the lepirudin-treated patients (29.4% vs. 9.1%, P = 0.0148). CONCLUSIONS: The rate of new TECs in HIT patients is low after start of lepirudin treatment. The rate of major bleeding of 17.6% might be reduced by reducing the starting dose to 0.1 mg kg(-1) h(-1).
BACKGROUND: Lepirudin (Refludan) is a hirudin derivative. It is a direct thrombin inhibitor obtained by recombinant technology from the medicinal leech and is approved for treatment of heparin-induced thrombocytopenia complicated by thrombosis. Because 3 cases of fatal anaphylaxis possibly associated with use of lepirudin have been reported, we initiated an investigation of putative lepirudin-associated anaphylaxis. METHODS AND RESULTS: Aided by the manufacturer (Schering AG, Berlin, Germany), we used the lepirudin study databases to identify all patients in whom possible anaphylaxis/severe allergy was recorded from 1994 to September 2002. The 26 possible cases identified were reviewed independently by 2 investigators. After excluding patients with mild skin reactions, reactions likely caused by concomitant medications, poorly documented cases, and reactions that did not correspond temporally with lepirudin use, there remained 9 patients judged to have had severe anaphylaxis in close temporal association with lepirudin. All reactions occurred within minutes of intravenous lepirudin administration, with 4 fatal outcomes (3 acute cardiorespiratory arrests, 1 hypotension-induced myocardial infarction). In these 4 cases, a previous uneventful treatment course with lepirudin was identified (1 to 12 weeks earlier). We recorded high-titer IgG-anti-lepirudin antibodies in an additional patient with anaphylaxis. Because lepirudin has been used in approximately 35 000 patients, the risk of anaphylaxis is approximately 0.015% (5 of 32 500) on first exposure and 0.16% (4 of 2500) in reexposed patients (7.5% estimated reexposures). CONCLUSIONS: Lepirudin can cause fatal anaphylaxis, particularly in patients who are treated within 3 months of a previous exposure. The overall risk/benefit assessment of lepirudin as a treatment for heparin-induced thrombocytopenia remains favorable.
BACKGROUND: The practicability and acceptance of written information about heparin thrombosis prophylaxis and the associated risk of heparin-induced thrombocytopenia (HIT) was evaluated in a pilot study. PATIENTS AND METHODS: All patients consecutively admitted to the department of trauma- and reconstructive surgery at the Ernst-Moritz-Arndt-University, Greifswald, Germany, with an indication for heparin thrombosis prophylaxis were give written information about thrombosis prophylaxis and the undesired drug effect HIT. After this, acceptance was evaluated using a standardized questionnaire. Primary endpoint was refusal of heparin for thrombosis prophylaxis, secondary endpoint acceptance and comprehensibility of the information. RESULTS: None of the 460 patients included in the study subsequently refused thrombosis prophylaxis with heparin. The majority welcomed the information and thought it should be given to all patients that are about to be treated with heparin. Only 0.9 % of patients judged comprehensibility of the information to be insufficient. Anticipation of imminent heparin therapy (good/very good in 90 %) and appreciation of the quality of care was not judged to be unacceptable by any patient. CONCLUSIONS: The present study demonstrates that giving information about heparin-induced thrombocytopenia during explanation of the risks and benefits of heparin thrombosis prophylaxis is feasible. This information--given in writing in our pilot study--was judged by patients to be comprehensible and necessary and did not lead to refusal of treatment. Lower incidence of HIT with use of low molecular weight heparins should be considered in the choice of drug for thrombosis prophylaxis.
BACKGROUND: Transmissible spongiform encephalopathies (TSEs) are neuropathological diseases caused by prions. Prions are infectious particles (PrPSc) which can induce bovine spongiform encephalopathy and most likely also the related infectious disease, variant of Creutzfeldt-Jakob disease (vCJD). The exposure of humans to orally ingested BSE agent in contaminated meat products presumably led to the emergence of vCJD. In vCJD, prions can be detected immunohistochemically not only in neuronal tissue but also in lymphoreticular tissue. vCJD is of significance in transfusion medicine because of the hypothetical transmission of prions by blood products. METHODS: An immunohistochemistry method was used to allow screening for vCJD in human lymphoreticular tissue. RESULTS: PrPSc can be detected in the cerebrum and cerebellum of patients with sporadic Creutzfeldt-Jakob disease (sCJD) and in the lymph nodes, tonsils, and spleen of vCJD patients. This method has the major advantage of working in fixed specimens which are routinely saved in departments of pathology and therefore allows screening of large numbers of archived human lymphoreticular tissues in different regional areas and from different time points. Scrapie-positive lymphoreticular sheep tissue reacts similarly to human tissue of vCJD affected patients and is available in sufficient amounts to be used as positive control in screening programs. CONCLUSION: A method is provided which is a feasible tool for an epidemiological screening program to assess the prevalence of the assumed infectious agent of vCJD, PrPSc, in various populations.
BACKGROUND AND OBJECTIVES: In the present article, we report on two patients with acute haemolytic transfusion reactions (AHTRs), and whom we were unable to transfuse, owing to alloantibodies that in vitro did not seem to be clinically significant. MATERIALS AND METHODS: The patients were a 67-year-old male and a 64-year-old female, both of whom developed antibodies to red blood cells (RBCs) after repeat blood transfusions. Serological analyses were carried out using standard techniques. RESULTS: Both patients developed an AHTR of the intravascular type following blood transfusions. Serological re-examination revealed weakly reactive alloantibodies with anti-JMH specificity in one patient, and with unclear specificity in the second. Rechallenging the patients with 15-30 ml of packed RBCs caused AHTRs, and blood transfusion became impossible in both cases. CONCLUSION: Weak alloantibodies that in vitro do not seem to be clinically significant may cause severe AHTRs.
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Approved indications for the recombinant hirudins lepirudin (Refludan(R)) und desirudin (Revasc(R)) are therapy of heparin-induced thrombocytopenia (HIT) and thrombosis prophylaxis following knee or hip replacement surgery. Kidney function dependent pharmacokinetics and their capability of inducing antibodies directed against hirudin are characteristic of this class of drugs. However, close dose-monitoring allows safe and effective use of both compounds. While lepirudin is used widely, besides danaparoid, for treatment of HIT, desirudin has not yet been widely accepted for thrombosis prophylaxis following knee or hip replacement surgery.
May-Hegglin anomaly (MHA) and Fechtner (FTNS) and Sebastian (SBS) syndromes are autosomal dominant platelet disorders that share macrothrombocytopenia and characteristic leukocyte inclusions. FTNS has the additional clinical features of nephritis, deafness, and cataracts. Previously, mutations in the nonmuscle myosin heavy chain 9 gene (MYH9), which encodes nonmuscle myosin heavy chain IIA (MYHIIA), were identified in all three disorders. The spectrum of mutations and the genotype-phenotype and structure-function relationships in a large cohort of affected individuals (n=27) has now been examined. Moreover, it is demonstrated that MYH9 mutations also result in two other FTNS-like macrothrombocytopenia syndromes: Epstein syndrome (EPS) and Alport syndrome with macrothrombocytopenia (APSM). In all five disorders, MYH9 mutations were identified in 20/27 (74%) affected individuals. Four mutations, R702C, D1424N, E1841K, and R1933X, were most frequent. R702C and R702H mutations were only associated with FTNS, EPS, or APSM, thus defining a region of MYHIIA critical in the combined pathogenesis of macrothrombocytopenia, nephritis, and deafness. The E1841K, D1424N, and R1933X coiled-coil domain mutations were common to both MHA and FTNS. Haplotype analysis using three novel microsatellite markers revealed that three E1841K carriers--one with MHA and two with FTNS--shared a common haplotype around the MYH9 gene, suggesting a common ancestor. The two new globular-head mutations, K371N and R702H, as well as the recently identified MYH9 mutation, R705H, which results in DFNA17, were modeled on the basis of X-ray crystallographic data. Altogether, our data suggest that MHA, SBS, FTNS, EPS, and APSM comprise a phenotypic spectrum of disorders, all caused by MYH9 mutations. On the basis of our genetic analyses, the name "MYHIIA syndrome" is proposed to encompass all of these disorders.
Clinical applications for recombinant hirudins have been investigated for the past 10 years. The first indication for which a hirudin-lepirudin-has been approved is treatment of heparin-induced thrombocytopenia (HIT). Also, the recently completed trials for use of lepirudin in unstable angina indicate a potentially new indication. This review describes pharmacology and clinical applications of lepirudin with an emphasis on HIT and unstable angina. An overview of usage of lepirudin in acute coronary syndromes is given, as well as a summary of rare indications for lepirudin, such as extracorporeal circulation, for which comprehensive data are lacking.
Transfusion related acute lung injury (TRALI) is a serious complication of blood transfusion, characterized by non-cardiogenic lung oedema. We describe a case of TRALI due to granulocyte-specific antibodies. The 58-year-old patient received 2 units of fresh frozen plasma following colon surgery and within 30 min the patient developed an acute respiratory distress syndrome. Granulocyte-specific antibodies were found in one of the transfused plasma of a female blood donor who most likely became immunized against granulocyte alloantigens during her three pregnancies.
Fechtner syndrome is a rare type of familial thrombocytopenia associated with large platelets, leukocyte inclusions, and features of Alport's syndrome. The bleeding tendency is usually mild, but severe hemorrhages have been reported. This is the case of a patient with Fechtner syndrome who was scheduled to undergo tonsillectomy. The patient had a history of easy bruising in childhood and a markedly prolonged bleeding time. Administration of DDAVP led to normalization of the bleeding time, and the patient underwent surgery without complications. With this approach the use of platelet concentrates could be avoided.