Therapie des Antiphosphoplidsyndrom (APS) mit DOAK

Das Antiphospholipid-Syndrom ist eine der schwerwiegendsten thrombophilen Störungen, die nicht nur zu rezidivierenden venösen, sondern auch zu arteriellen Thromboembolien sowie Schwangerschaftskomplikationen führen kann. Zusammen mit dem klinischen Bild ist das APS durch spezifische Laborbefunde charakterisiert: 1. Lupus Antikoagulans (LA), 2. Anticardiolipin-Antikörper (ACA), 3. β2-Glykoprotein I-Antikörper (β2GPI-AK). Alle Testergebnisse müssen nach 12 Wochen bestätigt werden. Sind alle drei Testgruppen positiv, besteht das höchste thrombotische Risiko. Beachtet werden muss, dass LA-Tests unter UFH, VKA oder DOAKs falsch positiv ausfallen können; bei DOAKs scheint die Zugabe von Absorbern nach Blutentnahme zuverlässige Ergebnisse zu liefern.

Eine Vergleichsstudie (TRAPS) zwischen VKA und dem DOAK Rivaroxaban mit ausschliesslich 3-fach positiven Hochrisiko-Patienten wurde vorzeitig abgebrochen, wegen erhöhter Ereignisraten unter Rivaroxaban [19 % zumeist arterielle Ereignisse versus 3 % unter Warfarin (HR 7.4; 1.7–32.9)]. Ein daraufhin herausgegebener Rote-Hand-Brief warnt vor der Anwendung von DOAKs bei Patienten mit APS, insbesondere bei Hoch-Risiko- (3-fach positiven) Patienten, und empfiehlt die Überprüfung einer laufenden DOAK-Therapie und eine mögliche Umstellung auf VKA, insbesondere bei Hoch-Risiko-Patienten. Als Fazit soll 1. bei klinischem Verdacht eine sorgfältige APS-Diagnostik erfolgen. Viele Patienten haben aufgrund von inadäquater Diagnostik wahrscheinlich gar kein APS und können bei venöser Thromboembolie adäquat ein DOAK erhalten.

2. Bei einfach- oder zweifach-positiven Antiphospholipid-AK Tests ohne LA besteht ein vergleichbar niedriges Thromboserisiko; auch hier kann möglicherweise ebenfalls mit DOAKs behandelt werden, wenn venöse Thrombosen vorliegen – ausreichende Daten liegen noch nicht vor, aber Metaanalysen legen dies nahe. 3. Patienten mit Positivität in allen 3 APS-Tests und APS-Patienten mit arteriellen Thromboembolien haben ein sehr hohes Risiko. Die TRAPS-Studie zeigt, dass diese Patienten nicht mit DOAKs, sondern mit einem VKA behandelt werden sollen.

[Modern treatment of deep vein thrombosis and pulmonary embolism]

Virchow's triad has been known for a 100 years. The development of therapeutic possibilities during this time was enormous. Today anticoagulant therapy is much more differentiated. Four new oral substances have replaced the traditional treatment with vitamin K antagonists in angiology. A standardized dosage is available. The monitoring of the coagulation parameters is no longer necessary, but it is important to monitor renal function. Direct oral anticoagulants are approved for the treatment of venous thrombosis and pulmonary embolism, but not during pregnancy or in children. Severe bleeding complications, especially intracerebral bleeding, are less common. The incidence of venous thromboembolism is still high. Obesity and cancer are of particular importance. The "therapeutic pact" with the patient requires that physicians master the art of "talking medicine".

International Council for Standardization in Haematology (ICSH) Recommendations for Laboratory Measurement of Direct Oral Anticoagulants

This guidance document was prepared on behalf of the International Council for Standardization in Haematology (ICSH) for providing haemostasis-related guidance documents for clinical laboratories. This inaugural coagulation ICSH document was developed by an ad hoc committee, comprised of international clinical and laboratory direct acting oral anticoagulant (DOAC) experts. The committee developed consensus recommendations for laboratory measurement of DOACs (dabigatran, rivaroxaban, apixaban and edoxaban), which would be germane for laboratories assessing DOAC anticoagulation. This guidance document addresses all phases of laboratory DOAC measurements, including pre-analytical (e.g. preferred time sample collection, preferred sample type, sample stability), analytical (gold standard method, screening and quantifying methods) and post analytical (e.g. reporting units, quality assurance). The committee addressed the use and limitations of screening tests such as prothrombin time, activated partial thromboplastin time as well as viscoelastic measurements of clotting blood and point of care methods. Additionally, the committee provided recommendations for the proper validation or verification of performance of laboratory assays prior to implementation for clinical use, and external quality assurance to provide continuous assessment of testing and reporting method.

Heparin-induced skin lesions

Cutaneous reactions to subcutaneous heparin injections have been described first in 1952. These reactions may be caused by several mechanisms such as immediate or delayed-type hypersensitivity responses, or by life-threatening immune-mediated heparin-induced thrombocytopenia (HIT). In contrast to bleeding, induction of osteoporosis and hair loss, no data on the incidence and causes of heparin-induced skin lesions had been available until recently. In a large prospective epidemiological study, the incidence of heparin-induced skin lesions was as high as 7.5% in medical patients, far exceeding the expected incidence. As heparin-induced skin lesions may be the sole clinical manifestation of immune HIT, rapid and valid diagnosis of heparin-induced skin lesions is of utmost clinical importance. Therefore, we have reviewed all known causes of heparin-induced skin lesions, and propose diagnostic and therapeutic procedures.

Diagnosis of heparin-induced delayed type hypersensitivity

Heparin is commonly used for prevention and therapy of thromboembolic diseases. Recently, work from a prospective epidemiological investigation has indicated, that heparin-induced skin lesions may be more frequent, than expected. Commonly, delayed-type hypersensitivity reactions can be identified as the cause of heparin-induced skin lesions. Rarely, immediatetype hypersensitivity responses or immune-mediated heparin-induced thrombocytopenia (HIT) are diagnosed. It is of clinical importance to differentiate between those, as patient management is fundamentally different. Patients, methods: We evaluated diagnostic procedures used to identify causes of heparin-induced skin lesions. Based on clinical presentation, histology and/or allergologic testing in 32 patients, heparin-induced delayed-type hypersensitivity (HIHS) was diagnosed. Results: Sensitivity of histology and s.c. provocation was high, amounting to 100% or 78% respectively. All other tests were unspecific or had a low sensitivity: Immediate readings of prick tests were false negative in 81%. Patch, prick and i.c. testing had a sensitivity ranging from 3.1–15.6%. Conclusion: Based on these results and despite the limitations of histology we recommend performing a skin biopsy rather than allergologic testing for diagnosis of HIHS. Compared to allergologic testing, results from histology are sensitive, readily available and may allow a differentiation from other causes of heparin-induced skin lesions.

Peak and baseline concentrations of fondaparinux during prophylactic therapy

Fondaparinux is widely approved for prophylaxis and treatment of venous thromboembolic events (VTE). However, its longer half-life time compared to heparins limits its peri-procedural use.

Aim: To investigate 3h peak and 24h baseline concentrations of fondaparinux when administered for prophylaxis (1 x 2.5 mg qd). Secondary outcome measures: incidences of VTE, bleedings, HIT, allergic skin reactions, 30 days mortality.

Patients, methods: Between 02/2010 and 03/2011, 3h peak and 24h baseline levels of fondaparinux were measured with a chromogenic anti-FXa method in 75 consecutive patients. Medical data were obtained from patients' records.

Results: The 5% and 95% percentile of the 3h peak level were 0.20 μg/ml and 0.83 μg/ml (median: 0.53 μg/ml), and of the 24h baseline level 0.08 μg/ml and 0.53 μg/ml (median 0.21 μg/ml), respectively. An inverse correlation was found between fondaparinux levels and GFRs (rho=-0.617 (3h); rho=-0.648 (24h); p=0.01). Shorter (≤5 days) or longer (≥8 days) duration of prior fondaparinux exposure showed no significantly different 3h peak/24h baseline levels (p>0.6). One progressive thrombosis occurred but no major bleedings, HIT, allergic skin reactions or fatalities.

Conclusions: After fondaparinux exposure, >75% of the patients still had relevant prophylactic 24h baseline levels. This did not coincide with a high rate of bleeding events. Due to the low patient number in this study undergoing surgery or interventions, it remains to be investigated whether or at which concentrations the bleeding risk is increased when baseline levels are within prophylactic ranges.

Blutungsrisiko und Blutungsnotfälle unter Rivaroxaban

Rivaroxaban, the first direct factor-Xa inhibitor anticoagulant, has been approved for the prevention of venous thromboembolism in adult patients undergoing elective hip or knee replacement surgery, for stroke prophylaxis in patients with non-valvular atrial fibrillation and for the treatment of deep vein thrombosis. There is no requirement for coagulation monitoring with rivaroxaban in routine clinical practice. However, in certain clinical circumstances such as life-threatening bleeding or an emergency operation the measurement of the thromboplastin time with a sensitive reagent will deliver first information. A quantitative determination of rivaroxaban plasma concentration is possible using an anti-factor Xa assay.

In the case of a patient under long-term anticoagulation with rivaroxaban requiring an elective surgery, a discontinuation of rivaroxaban 20 to 30 hours before the operation is sufficient to normalize the associated bleeding risk, as long as the renal and liver function is normal. A longer interval should be taken into consideration, when the patient presents a renal and liver impairment or is of a higher age. In the event of an emergency operation effective rivaroxaban concentrations might be present. Nevertheless, we advise against using a prophylactic dose of factor concentrates. Recommendations: From a clinical perspective, in the event of a minor bleeding we recommend a temporary discontinuation of rivaroxaban, whereas for clinically relevant major or severe bleeding events a mechanical compression or a limited surgical i. e. interventional treatment is required. Supportive measures such as the administration of blood products or tranexamic acid might be beneficial. In addition to haemodynamic supportive measures life threatening bleeding events demand a comprehensive haemostasis management, as well as the application of PCC.

Therapie mit Dabigatran

Summary Dabigatran, an oral, reversible direct factor IIa inhibitor, is approved in Europe for stroke prevention in atrial fibrillation and for the prevention of venous thromboembolism after elective hip and knee replacement. In contrast to vitamin K antagonists, a routine coagulation monitoring during the treatment with dabigatran etexilate is not necessary. However, in specific clinical situations such as invasive emergency procedures or serious haemorrhage, the actual anticoagulant status of dabigatran may be of importance for the treating clinician and can be assessed by clotting tests (aPTT, TT, ECT). The diluted thrombin time test (Hemoclot®), which is specifically calibrated for dabigatran, is useful for quantitative determination of the dabigatran serum concentration. In general, discontinuation of dabigatran etexilate 24 hours before standard elective surgery is sufficient to normalise the bleeding risk in patients with normal renal function. In patients with renal impairment and/or in the case of a high bleeding risk procedure the recommended duration of discontinuation is prolonged. If a bleeding episode occurs in a patient on dabigatran, further treatment should be based on the severity and localisation of the bleeding. A distinct feature of dabigatran is the possibility of effectively removing dabigatran from the circulation by haemodialysis. Recommendation: In the case of clinically minor bleedings, a delay in the administration of the next dabigatran etexilate dose is recommended. The length of the delay is based on the patient’s individual thromboembolic risk. In minor bleedings the use of prothrombin complex concentrates is not indicated. In the case of moderate or major bleedings the main focus should be on stabilising the circulation by using fluids and blood products and, if a lesion can be identified, the local treatment thereof. If time and infrastructure is available, dialysis offers an effective and fast option to remove dabigatran out of the circulation. In the incidence of severe and life threatening bleedings, an additional, more complex haemostasis management is required. Besides haemodynamic stabilisation of the circulation, administration of prothrombin complex concentrates should not be delayed. It has to be kept in mind that standard laboratory coagulation parameters may not accurately reflect the effect of prothrombin complex concentrates in patients on dabigatran. Hence the effect of the prothrombin complex concentrate should be monitored clinically and adjusted by means of onset of coagulation in vivo.

Direct oral anticoagulants (DOAC) - Management of emergency situations

The worldwide increase in the aging population and the associated increase in the prevalence of atrial fibrillation and venous thromboembolism as well as the widespread use of direct oral anticoagulants (DOAC) have resulted in an increase of the need for the management of bleeding complications and emergency operations in frail, elderly patients, in clinical practice. When severe bleeding occurs, general assessment should include evaluation of the bleeding site, onset and severity of bleeding, renal function, and concurrent medications with focus on anti-platelet drugs and nonsteroidal anti-inflammatory drugs (NSAID). The last intake of the DOAC and its residual concentration are also relevant. The site of bleeding should be immediately localized, anticoagulation should be interrupted, and local measures to stop bleeding should be taken. In life-threatening bleeding or emergency operations immediate reversal of the antithrombotic effect may be indicated. If relevant residual DOAC-concentrations are expected and surgery cannot be postponed, prothrombin complex concentrate (PCC) and/or a specific antidote should be given. While idarucizumab, the specific antidote for dabigatran, has been recently approved for clinical use, the recombinant factor X protein andexanet alfa, an antidote for the reversal of inhibitors of coagulation factor Xa, and ciraparantag, a universal antidote, are not available. Future cohort studies are necessary to assess the efficacy and safety of specific and unspecific reversal agents in "real-life" conditions. This was the rationale for introducing the RADOA-registry (RADOA: Reversal Agent use in patients treated with Direct Oral Anticoagulants or vitamin K antagonists), a prospective non-interventional registry, which will evaluate the effects of specific and unspecific reversal agents in patients with life-threatening bleeding or emergency operations either treated with DOACs or vitamin K antagonists.

Fortschritte in der Thrombozytenfunktionsdiagnostik

Both for diagnosis of congenital and acquired platelet dysfunction as well as for therapy monitoring after application of platelet function inhibitors various methods have been established for evaluation of platelet function. In contrast to the gold standard of platelet function testing, the light transmission aggregometry in platelet rich plasma the Point-of-care (POC) analyzers allow fast analysis of platelet function without extensive laboratory work up. The conditions of the pre-analytical phase, however, are still of enormous importance in the prevention of medical errors. There is increasing clinical data in monitoring the effect of platelet aggregation inhibitors, showing that quantitative determination of the platelet function degree correlates with risk of increased bleeding or stent thrombosis. However, it is still unclear, which is the optimal test system, to predict the clinical outcome of these patients.

Danaparoid in der Schwangerschaft bei Heparinunverträglichkeit

Unter Therapie mit unfraktioniertem oder niedermolekularem Heparin treten häufig unerwünschte Arzneimittelwirkungen auf, die eine Fortsetzung der Therapie unmöglich machen. Insbesondere bei Schwangeren mit thromboembolischen Komplikationen kann es schwierig sein, ein geeignetes alternatives Antikoagulans zu finden, wenn zusätzlich eine Heparinunverträglichkeit vorliegt. Für den Einsatz von Danaparoid in der Schwangerschaft gibt es nur wenige Daten. Die Hauptgründe in den untersuchten 59 Schwangerschaften für eine Heparinunverträglichkeit waren entweder eine HIT II bei 37/59 (62,7%) Schwangeren, oder eine kutane Nebenwirkung in 19/22 (86,4%) der nicht HIT-assoziierten Schwangerschaften (22/59, 37,3%). Ergebnisse: 40/59 Schwangerschaften konnten unter Danaparoid erfolgreich ausgetragen werden, bei 16/19 wurde die Therapie aufgrund unerwünschter Arzneimittelwirkungen beendet. Fünf Patientinnen zeigten Blutungskomplikationen, die ebenso wenig Danaparoid-assoziiert waren wie die berichteten sechs Aborte und eine Abruptio. In 31/59 (52,5%) Schwangerschaften traten unerwünschte Arzneimittelwirkungen auf, 14/31 (45,2%) ließen sich auf Danaparoid zurückführen. In fünf Nabelschnurblut- und vier Brustmilchproben konnte keine Anti- Xa-Aktivität gemessen werden. Schlussfolgerung: Danaparoid kann zur alternativen Antikoagulation bei Schwangeren mit hohem Thromboserisiko und Heparinunverträglichkeit eingesetzt werden.

Überwachung der Antikoagulanzientherapie mit Fondaparinux

Im Gegensatz zu niedermolekularem und unfraktioniertem Heparin besitzt Fondaparinux, ein synthetisch hergestelltes Pentasaccharid, einen selektiv hemmenden Effekt auf den Gerinnungsfaktor X. Die Substanz ist seit drei Jahren zur Hochrisikothromboseprophylaxe nach großen orthopädischen Operationen zugelassen. Auf Grund der ausgezeichneten Bioverfügbarkeit nach subkutaner Gabe, die einmal pro Tag in körpergewichtsunabhängiger Dosierung (bei einem Körpergewicht von 50-100 kg) erfolgen kann, ist normalerweise ein Monitoring nicht erforderlich. Insbesondere seit der europaweiten Zulassung zur Therapie venöser Thrombosen ist jedoch im Ausnahmefall (z. B. Verdacht auf Fehldosierung, bei Niereninsuffizienz oder Blutungen) ein Monitoring im Routinelabor sinnvoll.

Inzwischen wurden chromogene Substratmethoden, basierend auf zur Verfügung stehenden Monitoring-Methoden zur Messung des Faktor Xa inhibierenden Effektes der niedermolekularen Heparine, publiziert. Unter Berücksichtigung dieser Publikationen sollte Fondaparinux als Kalibrator verwendet und die Einheiten in μg/ml angegeben werden. Wegen der synthetischen Herstellung der Substanz findet sich eine lineare Dosis/Wirkungsbeziehung in einem weiten Konzentrationsbereich, so dass eine sehr gute Präzision der Methodik an Vollautomaten erreicht werden kann.

Resistenz gegen Azetylsalizylsäure und Clopidogrel

Resistenz gegen Azetylsalizylsäure (ASS) bzw. Clopidogrel wird vom klinischen Gesichtspunkt als Unvermögen des Wirkstoffs angesehen, rezidivierende arterielle Gefäßverschlüsse zu verhindern. Aus laborchemischer Sicht hingegen wird die Non-Response gegenüber ASS und Clopidogrel als das Ausbleiben eines erwarteten Effektes in verschiedenen Thrombozytenfunktionstestsystemen beschrieben. Etablierte Thrombozytenfunktionsteste ermöglichen meist keine spezifischen Aussagen über die Thrombozytenaggregationshemmung durch ASS oder Clopidogrel. Wünschenswert wäre, die ASS- und Clopidogrel-Non-Response mit Plättchenfunktionstesten derart zu ermitteln, dass isoliert die spezifischen Effekte dieser Arzneimittel erfasst werden. Im Idealfall könnte eine solche Labordiagnostik helfen, klinische Ereignisse aufgrund eines Therapieversagens im Vorfeld zu verhindern. Studien, die eine Prävalenz von 5 bis 59% für die ASS- oder Clopidogrel-Non-Response angeben, geben erste Hinweise dafür, dass der Nachweis einer laborchemischen ASS- oder Clopidogrel-Non-Response mit dem nachfolgendem Auftreten vaskulärer Reereignisse assoziiert sein könnte. Allerdings sind diese Studien durch zu geringe Fallzahlen, fehlende Standardisierung der Labormethoden und sehr differente Einschlusskriterien in ihrer Aussagekraft limitiert. Deshalb bleibt die klinische Relevanz laborchemisch nachgewiesener ASS- oder Clopidogrel- Resistenz unklar und sollte umgehend in prospektiven Multizenterstudien geklärt werden. Die individuellen Ursachen einer reduzierten oder ausbleibenden Wirkung von ASS oder Clopidogrel können multifaktoriell sein. Die Mechanismen der ASS- bzw. Clopidogrel- Resistenz sind weitgehend ungeklärt.

Molecular weight determines the frequency of delayed type hypersensitivity reactions to heparin and synthetic oligosaccharides

Eczematous lesions, resulting from type IV sensitizations are well-known and relatively frequent cutaneous adverse effects of s.c. heparin therapy. If anticoagulation is further required intravenous heparin, heparinoids or lepirudin may be used as a substitute. However, these alternatives are not optimal in terms of practicability and/or safety-profiles. As molecular weight of different heparin preparations has repetitively been implied to determine the frequency of sensitization, we hypothesized, that due to its low molecular weight the pentasaccharide fondaparinux may provide a practicable and safe anticoagulant therapy in patients with delayed type hypersensitivity reactions (DTH) to heparin and other oligosaccharides. To test this concept, patients referred for diagnosis of cutaneous reactions after s.c. anticoagulant treatment underwent a series of in vivo skin allergyand challenge-tests with unfractionated heparin, a series of low molecular weight heparins (nadroparin, dalteparin, tinzaparin, enoxaparin and certoparin), the heparinoid danaparoid and the synthetic pentasaccharide fondaparinux. In total, data from twelve patients was evaluated. In accordance with previously published data, we report a high crossreactivity among heparins and heparinoids. In contrast – and in support of our initial hypothesis – sensitization towards the synthetic pentasaccharide fondaparinux was rarely observed. Plotting the cumulative incidence against the determined molecular weight of the individual anticoagulant preparations, shows that molecular weight generally is a key determinant of sensitization towards heparins and other oligosaccharides (r2=0.842, p=0.009). Hence, fondaparinux may be used as a therapeutic alternative in patients with cutaneous DTH relations towards heparin and other polysaccharides.

Management of cutaneous type IV hypersensitivity reactions induced by heparin

Localized hypersensitivity reactions to subcutaneous heparin injections have been described since 1952. Yet, the incidence of these reactions, which are distinct from skin lesions associated with heparin-induced thrombocytopenia type II (HIT II), remains uncertain. However, in the last 10 years an increasing number of patients have been reported, leading to the assumption that cutaneous hypersensitivity reactions towards heparin are underreported. Clinically patients present with itching, sometimes infiltrated, and blistering erythemas at the injection sites of heparins. The diagnosis of cutaneous heparin allergy may, on the one hand, lead to delay of required medical or surgical treatment. On the other hand, delayed initiation of treatment may lead to a generalized eczematous reaction. Hence, from review of 223 cases of patients with cutaneous hypersensitivity reactions to heparin, we here summarize the clinical picture of cutaneous type IV allergic reactions, define risk factors on both the patient- and drug-side, and give an overview of principle therapeutic alternatives, as well as recommendations for treatment options for emergency and elective patients. As the proposed management of patients with cutaneous hypersensitivity reactions to heparin may have fatal consequences when applied in patients with HIT type II, diagnosis of skin lesions in heparin-treated patients needs to be precise.

Association of ADAMDEC1 haplotype with high factor VIII levels in venous thromboembolism

A suggestive locus on chromosome 8 could be shown to be associated with familial high factor VIII (FVIII) levels in venous thromboembolism. The ADAMDEC 1 gene is a candidate expressing an ectodomain sheddase. However, the ectodomain of the clearance receptor for FVIII, the low-density lipoprotein receptor-related protein (LRP), is subject to proteolysis by metalloproteases like ADAMDEC1. Other LRP-interacting proteins are lipoprotein lipase (LPL) and t-PA. For an association study, 165 thrombotic patients with high FVIII levels (from the MAISTHRO, i.e. Main-Isar-thrombosis register) were included. All patients with known causes for high FVIII levels had been previously excluded. The patients were compared with 214 healthy blood donors. Polymorphisms with usually a minor allele frequency > 5 %, i.e. 24 SNPs and two insertion/deletion polymorphisms of LPL gene, eight SNPs of the t-PA gene, and five SNPs of the ADAMDEC1 gene, were analyzed. Haplotype differences were calculated using PHASE. A new polymorphism in intron 7 of the t-PA gene with a minor allele frequency of 2.2% was identified. Analysis of each SNP by the Cochrane-Armitage trend test did not show any significant association between genotype and disease status. Interestingly, the ADAMDEC1 haplotype (rs12674766, rs10087305, rs2291577, rs2291578, rs3765124) differed between cases and controls (p=0.04). In particular, the TGTGG haplotype showed a difference. In conclusion, the ADAMDEC 1 haplotype may indicate an underlying mechanism for high FVIII levels. The only moderate linkage disequilibrium may be due to a possible causal polymorphism in distant introns or the promoter region against a polygenic background.

Ex vivo effects of low-dose rivaroxaban on specific coagulation assays and coagulation factor activities in patients under real life conditions

Global coagulation assays display variable effects at different concentrations of rivaroxaban. The aim of this study is to quantify the ex vivo effects of low-dose rivaroxaban on thrombophilia screening assays and coagulation factor activities based on the administration time, and to show how to mask possible interferences. Plasma samples from 40 patients receiving rivaroxaban 10 mg daily were investigated to measure activities of clotting factor II, V, VII, VIII, IX, XI, XII and XIII; protein C- and protein S-levels; lupus anticoagulants; anticardiolipin IgG and IgM; D-dimer, heparin-platelet factor 4 (HPF4) antibodies and screening tests for von Willebrand disease (VWD). Two hours after rivaroxaban administration, the activities of clotting factors were significantly decreased to different extents, except for factor XIII. Dilution of plasma samples resulted in neutralisation of these interferences. The chromogenic protein C activity assay was not affected by rivaroxaban. Depending on the timing of tablet intake in relation to blood sampling protein S activity was measured falsely high when a clotting assay was used. False-positive results for lupus anticoagulants were observed depending on the assay system used and the administration time of rivaroxaban. ELISA-based assays such as anticardiolipin IgG and IgM, D-dimer, HPF4-antibodies and the turbidimetric assays for VWD were not affected by rivaroxaban. Specific haemostasis clotting tests should be performed directly prior to rivaroxaban intake. Assay optimisation in the presence of rivaroxaban can be achieved by plasma dilution. Immunologic assays are not influenced by rivaroxaban, while chromogenic assays can be used, when they do not depend on factor Xa.

Rivaroxaban differentially influences ex vivo global coagulation assays based on the administration time

It was the objective of this study to quantify the effects of rivaroxaban administration on global coagulation parameters associated with routine clinical procedures, we collected plasma samples from patients undergoing major orthopaedic surgery receiving rivaroxaban at various time points after drug administration. Forty-seven patients received rivaroxaban (10 mg daily) for venous thromboembolism prophylaxis. Blood samples were collected at four different time points: A) before surgery; B) before drug administration at day 4–5 after surgery (steady state of rivaroxaban); C) 2 hours (h) after drug administration and D) 12 h after drug administration. The prothrombin time (PT), activated partial thromboplastin time (aPTT), thrombin time (TT), antithrombin (AT) level, fibrinogen level by Clauss method (FibC), and derived fibrinogen (dFIB) level were assessed with various reagents. At 2 h after rivaroxaban administration, the PT and aPTT clotting times were significantly prolonged to different extents up to 1.4 fold, whereas 12 h after drug administration, no significant effect was observed. Rivaroxaban administration had no influence on the TT or the FibC concentration. The dFIB assay was differentially affected by rivaroxaban when different reagents were tested. The AT assay dependent on thrombin activity was not influenced by rivaroxaban, whereas the AT levels dependent on factor Xa activity were significantly increased by rivaroxaban. Clinicians should be aware of the time-dependent influence of rivaroxaban on factor Xa-dependent routine coagulation assays. Therefore, routine coagulation parameters should be assessed directly before drug administration to keep the interaction of rivaroxaban low.

Hereditary and acquired thrombophilia in patients with upper extremity deep-vein thrombosis

The prevalence of coagulation disorders in patients with upper extremity deep-vein thrombosis (UE-DVT) is unknown due to only a few observational studies of limited size reporting varying results. Therefore, we aimed to evaluate the prevalence of thrombophilia in patients with UE-DVT compared to patients with lower extremity deep vein thrombosis (LE-DVT). One hundred fifty consecutive patients (15 to 91 years of age) with UE-DVT were recruited from the MAISTHRO (MAin-ISar-THROmbosis) registry. Three hundred LE-DVT patients matched for gender and age served as controls. Thrombophilia screening included tests for the factor V Leiden mutation, the prothrombin G20210A mutation, antiphospholipid antibodies and factor VIII (FVIII), protein C, protein S and antithrombin activities. At least one thrombophilia was present in 34.2% of UE-DVT and 39.2% in UE-DVT that was unrelated to venous catheters relative to 55.3% in LE-DVT patients (p<0.001). In particular, a persistently elevated FVIII is less likely to be found in UE-DVT patients than in those with LE-DVT and is the only thrombophilia that is differentially expressed after controlling for established VTE risk factors [OR 0.46, (95% CI 0.25–0.83)]. Although less prevalent than in LE-DVT patients, thrombophilia is a common finding in patients with UE-DVT, especially in those with thrombosis that is unrelated to venous catheters.