[Incidental finding of pathological coagulation parameters]. / Zufallsbefund pathologischer Gerinnungsparameter.

Pathological coagulation parameters may reflect life-threatening hemorrhagic or thromboembolic diseases but may also be a laboratory result without any clinical significance, result from in vitro phenomena or preanalytical errors. This article gives an overview of potential pitfalls in coagulation diagnostics, lists the differential diagnoses of pathological coagulation parameters and describes further steps in the diagnostic approach to clarify pathological results. The focus lies on coagulation parameters that are frequently determined in routine clinical investigations, e.g. platelet count, prothrombin time, activated partial thromboplastin time (aPTT) and fibrinogen. Besides heparin, fondaparinux, danaparoid, and vitamin K antagonists, direct factor Xa inhibitors and direct thrombin inhibitors are nowadays available for therapeutic anticoagulation. This article gives an overview of the influence of anticoagulants on coagulation parameters which depends on the dose, the time of the last administration, as well as the method used for the determination of coagulation parameters. Moreover, common reasons for elevation of the fibrin degradation product D-dimer are presented. The clinical utility of D-dimer assays is limited by their poor specificity. Elevated D-dimer concentrations can be found in various diseases and also under normal physiological circumstances (e.g. in the elderly). Thus, the most useful clinical application of D-dimer is evidence of normal values to essentially rule out venous thromboembolism.

Deferrals of volunteer stem cell donors referred for evaluation for matched-unrelated stem cell donation.

To minimize donor risk and maintain public support, volunteer donor stem cell donation, whether by mobilized leukapheresis or marrow aspiration, requires careful donor eligibility assessment. Many contraindications to stem cell donation exist, yet analyses of donor deferral rates are not available. In a 36-month series encompassing 2493 potential stem cell donors, we analyzed frequencies and reasons for deferrals. All were presumed eligible by their registries because of previously submitted structured health questionnaire and formal telephone interviews. After assessment by our center's physicians, 3.3% of donors proved ineligible, but 5.6% more were eligible for only one of the collection methods. Higher deferral rates were associated with female sex, increasing age and mobilized stem cell donation vs marrow. Exclusion criteria were identified with approximately similar frequency by medical history, physical examination and laboratory testing. Reasons for deferrals almost exclusively served to protect donor safety; the rare recipient-directed safety concerns could be, and often were, overridden in agreement with the transplant center. As formal analyses have shown, with careful assessment, stem cell donation is acceptably safe, but the plethora of deferral reasons mandate that only physicians with specific experience should evaluate stem cell donors, that is, this task should not be delegated to paramedical personnel.

Evidence-based indications for thrombophilia screening.

Thrombophilic defects have been shown to be associated with an increased risk of venous thrombosis, fetal loss, and gestational complications. The knowledge about the clinical relevance of thrombophilic defects is increasing, and evidence-based indications for thrombophilia screening are therefore discussed in this review. Selective thrombophilia screening based on previous personal and/or family history of venous thromboembolism is more cost-effective than universal screening in all patient groups evaluated. In the majority of patients with acute venous thrombosis, the results of thrombophilia screening do not influence the duration of oral anticoagulation. The only patient population who clearly profits from thrombophilia screening in this situation are patients with a newly diagnosed antiphospholipid syndrome, because prolonged anticoagulation can avoid the high incidence of recurrence in this patient population. Because of the increased risk of venous thrombosis during pregnancy and the puerperium, thrombophilia screening is indicated in selected patients with a previous history of venous thrombosis or a positive family history. Significant associations with early and late pregnancy loss are observed for carriers of the heterozygous factor V Leiden mutation, the heterozygous prothrombin-mutation G20210A and anticardiolipin antibodies, while protein S deficiency is significantly associated with late pregnancy loss. Antithrombotic drugs like UFH, LMWH or low-dose aspirin may have a potential therapeutic benefit in patients with recurrent pregnancy loss and thrombophilia, but placebo-controlled, multicenter trials are urgently needed to clarify this issue. Although a supra-additive effect for the risk of venous thrombosis is observed between oral contraceptives and some thrombophilias, the absolute incidence of venous thromboembolism is low in premenopausal women and mass screening strategies are therefore unlikely to be effective. While antiphospholipid antibodies are known to be associated with arterial thrombosis, screening for heritable thrombophilias is not useful in arterial thrombosis, although subgroup analysis indicates that they may play a role particularly in young patients and children.

[Update thrombophilia]. / Update Thrombophilie.

A survey on definitions, epidemiology, clinical manifestations of congenital and acquired thrombophilias is given with focus on evidence-based data. Diagnostic and therapeutical strategies are presented. Selective thrombophilia screening based on previous personal and/or family history of venous thromboembolism is more cost-effective than universal screening in all patient groups. In the majority of patients with venous thrombosis the results of thrombophilia screening do not influence the duration of oral anticoagulation. The only patient population who clearly profits from thrombophilia screening in this situation are patients with a newly diagnosed antiphospholipid syndrome, because prolonged anticoagulation can avoid the high incidence of recurrence in this patient population. Because of the increased risk of venous thrombosis during pregnancy and the puerperium, thrombophilia screening is indicated in selected patients with a previous history of venous thrombosis to be able to decide whether anticoagulation is necessary when these patients become pregnant. Significant associations with early and late pregnancy loss are observed for patients with thrombophilia while it remains unknown whether these patients profit from anticoagulation with heparin or low dose aspirin during their next pregnancy since placebo-controlled multicenter trials are not yet available.

[Genomic diagnosis of thrombophilia in women: clinical relevance]. / Genomische Diagnostik thrombophiler Gerinnungsstörungen bei Frauen: Klinische Relevanz.

The detection of the DNA-sequence of human coagulation factors and inhibitors has introduced the possibility of differentiated mutation analysis in patients with venous thrombosis. Since venous thromboembolism is a multifactorial disease, women are at an increased risk to develop venous thrombosis due to hormonal contraception, during pregnancy and the puerperium. In addition, pregnancy complications like early or late fetal loss, pregnancy-induced hypertensive disorders and very recently recurrent embryo implantation failure have been suspected to be associated with thrombophilia. Therefore, it is of major importance to define inherited thrombophilic disorders, in which genetic diagnosis is of clinical relevance. While most of the genetic defects described so far represent a risk factor for venous thrombosis, only a minority of these defects actually needs DNA analysis to be detected: mutation analysis is clinically relevant, when factor V Leiden mutation is suspected, because relative risks concerning venous thrombosis as well as pregnancy complications clearly differ between homozygote and heterozygote forms of this frequently observed mutation. Similarly detection of the prothrombin mutation G20210A is of clinical relevance, although data for the very rarely observed homozygote variant are not sufficiently available. In contrast, detection of the homozygote variant of the MTHFR-mutation C677T is not useful, since clinical relevance could not be proven in a majority of studies concerning women specific risk situations. Inherited deficiencies of antithrombin, protein C and protein S are rare with high rates of different mutations. Genetic analysis seems only useful in patients with wide intraindividual variations of coagulation inhibitor activities. Genetic analysis concerning the PAI-1 4G/5G polymorphism or the factor XIII Val34Leu polymorphism can not be recommended in women specific risk situations because of insufficient data.

Development and clinical evaluation of two chromogenic substrate methods for monitoring fondaparinux sodium.

This study was designed to develop methods for monitoring of the selective factor Xa inhibitor fondaparinux sodium (ARIXTRA) based on standard laboratory methods for the chromogenic determination of the anti-factor Xa activity of low molecular weight heparin. To examine the biologic activity of fondaparinux in comparison to its plasma concentration, 2 methods were investigated: 1 working with the addition of antithrombin (AT), the other without exogenous AT. Both methods showed a linear relationship of fondaparinux concentration and OD/min on a log-lin scale in the range from 0.1 to 2 microg/mL. Inter- and intra-assay variability was <6% in all cases. The results of spiked samples from patients on vitamin K antagonists (VKA) were in good agreement with both methods, and the determination of the fondaparinux concentration was not influenced by reduced levels of factor X in plasma caused by VKA-intake. Ex vivo samples from orthopedic patients (n=18) on prophylactic treatment with fondaparinux showed concentrations between 0.2 to 0.7 microg/mL 3 hours after s.c. injection. No significant differences were detected between both methods with these samples. The presented methods are suitable tools for monitoring of fondaparinux. The linear calibration curve in the range 0.1 to 2 microg/mL is suitable for determination of prophylactic and therapeutic application of fondaparinux. Both methods, with and without addition of AT, can be performed fully automated in clinical routine on an automated coagulation analyzer (STA coagulation analyzer). No significant differences were detected between both methods with these samples.

[Malignancy and thrombosis: a double-sided clinical relationship]. / Malignom und Thrombose: eine wechselseitige klinische Beziehung.

Venous thromboembolism (VTE) is the second most common cause of mortality in cancer patients and also points towards unfavourable prognosis. In about 10% of patients with idiopathic VTE there is underlying malignancy. However, the efficacy of extensive tumour screening in those patients is not yet established. Numerous plasmatic and cellular components contribute to the phenomenon of hypercoagulability in cancer patients, including Cancer Procoagulant and activation of coagulation with high levels of coagulation factors. Cancer surgery carries an increased risk compared to non-cancer patients necessating more intensive and longer thromboprophylaxis in those patients. In medical patients active cancer is associated with increased risk for VTE. In the treatment of VTE, cancer patients have a significantly higher recurrence rate for VTE when treated with vitamin K-antagonists (VKA) compared to non-cancer patients. Compared to VKA the use of low molecular weight heparin for long-term secondary prevention is more effective than vitamin K-antagonists. Thus, there is a grade 1A recommendation to use low molecular weight heparin for cancer patients during the first 3-6 months of secondary prevention of VTE. Several studies indicate that low molecular weight heparin may also improve the prognosis of cancer patients quoad vitam, particularly for cancer patients at an earlier stage of disease; this needs to be confirmed in further studies.

Use of native or platelet count adjusted platelet rich plasma for platelet aggregation measurements.

BACKGROUND: It is still not clear whether native or platelet count adjusted platelet rich plasma (PRP) should be used for platelet aggregation measurements. AIM: To evaluate the necessity of using adjusted PRP in platelet function testing. METHODS: Platelet aggregation with native PRP and adjusted PRP (platelet count: 250/nl, obtained by diluting native PRP with platelet poor plasma) was performed on the Behring Coagulation Timer (BCT(R)) using ADP, collagen, and arachidonic acid as agonists. Healthy subjects, patients on antiplatelet treatment, and patients with thrombocytosis (platelet counts in PRP > 1250/nl) were investigated. RESULTS: No significant differences in the maximum aggregation response were seen when using either native or adjusted PRP from healthy subjects and patients on antiplatelet treatment. Nevertheless, some patients taking aspirin or clopidogrel showed reduced inhibition of ADP and arachidonic acid induced aggregation in adjusted PRP but not in native PRP. The maximum velocity of healthy subjects and patients on antiplatelet treatment varied significantly as a result of the degree of dilution of the adjusted PRP. Surprisingly, the BCT provided good results when measuring platelet aggregation of native PRP from patients with thrombocytosis, whereas commonly used aggregometers could not analyse platelet aggregation of native PRP in these patients. CONCLUSION: The time consuming process of PRP adjustment may not be necessary for platelet aggregation measurements. Moreover, using adjusted PRP for monitoring aspirin or clopidogrel treatment may falsify results. Therefore, it may be better to use native PRP for platelet aggregation measurements, even in patients with thrombocytosis.

Influence of blood collection techniques on platelet function.

For investigations of platelet function it is recommended that venipuncture should be performed using ordinary needle systems instead of butterfly cannulae systems. Platelets might be activated in the long plastic tubes of butterfly systems. The aim of this study was to investigate the dependency of platelet function results on blood sampling using different collection systems. Therefore, blood of 25 healthy volunteers was collected from both arms using at the same time on one side a 21-gauge needle and on the other side a 21-gauge butterfly cannula system. Both samples of each volunteer were analyzed on the PFA-100. Platelet aggregation was performed on the Behring Coagulation Timer (BCT) and the optical aggregometer PAP-4 using ADP, collagen and arachidonic acid to induce platelet aggregation in platelet-rich plasma. No significant prolongation of the closure times on the PFA-100 with the COL/EPI cartridge and the COL/ADP cartridge was observed when using butterfly cannulae. The results of optical aggregometry were not significantly different. The maximum aggregation response did not differ significantly for both collection systems. Aggregometry and the PFA-100 system are not affected by different blood collection systems. Therefore butterfly cannulae can be used for sample collection to investigate platelet function.