[Modified platelet aggregation test in patients on ASA and/or clopidogrel]. / Kontrolle der Thrombozytenaggregations-hemmung unter Therapie mit Azetylsalizylsäure und/oder Clopidogrel mit einem modifizierten Thrombozytenaggregationstest.

Therapy with acetylsalicylic acid (ASA) and/or clopidogrel is used to achieve prophylactic inhibition of platelet aggregation in patients with arterial thrombosis. We examined if aggregometry can be used to see the effect of antiplatelet drugs (ASA 30, 50, 100, 300 mg/d, clopidogrel 75 mg/d or ASA 100 + clopidogrel 75 mg/d). A modified platelet aggregation test was used to investigate maximum aggregation in response to ADP, collagen, adrenalin and arachidonic acid. Reference values were established based on healthy individuals. We devised a simple scoring system for detection of inadequate platelet inhibition. Compared with the control group, we detected a significant delay of maximum aggregation in response to all agonists in patients on ASA and combination therapy ASA + clopidogrel. Patients on clopidogrel alone were found to have prolonged aggregation when induced with ADP, collagen and arachidonic acid. The failure rate to achieve adequate platelet inhibition on 100 mg/d ASA, 75 mg/d clopidogrel or combination therapy was 27%, 26% and 7%, respectively. Our results demonstrate that platelet inhibition in aggregometry is inadequate in many patients with arterial thrombosis.

[Hereditary factor V deficiency and factor V inhibitor without bleeding. Rare causes of pathological screening tests of coagulation]. / Hereditärer Faktor-V-Mangel und Faktor-V-Inhibitor ohne Blutungsneigung. Seltene Ursachen pathologischer Globaltests.

Isolated reduction in factor V activity either occur in form of a hereditary deficiency of factor V as an acquired inhibitor against factor V. Diagnosis can not be made by bleeding alone because in both cases it can occur or not occur. Two patients were investigated showing pathological screening tests of coagulation without bleeding. A hereditary and an acquired deficiency of factor V were proved.

[Plasma blood coagulation in mammals (domestic and zoo animals). Experience with screening tests and determinations of individual factor activities]. / Plasmatische Blutgerinnung bei Säugetieren (Haus- und Zootiere). Erfahrungen mit Globaltesten und Aktivitätsbestimmungen von Einzelfaktoren.

Plasma coagulation in mammals shows an essentially uniform structure. Differences are in species specific composition and quantity of coagulation factors. Many of the coagulation disorders occurring in humans have been observed in other mammals. Almost all the coagulation studies performed to date have been in domestic animals. For the majority of mammalian species, e.g. zoo animals, therefore, we have either no data at all or only isolated results. The methods used for coagulation testing in veterinary medicine have not yet been standardized. The significance and informative value of the screening tests are limited in animals compared with humans. The activities of individual factors in animals are determined by coagulometric tests. The results can be determined in relation to the activity in humans with the help of a human normal plasma or in relation to the activity of the respective animal with the help of a normal plasma from the same species. The problem is the parallelity of the dilution curves used as reference curves. The coagulation factor activities given for mammals usually differ more or less markedly from those in humans.

Increased risk of venous thromboembolism in patients with acute leukaemia.

Patients with malignancies have an increased risk for venous thromboembolisms (VTE), but data on patients with acute leukaemia are very limited so far. We found VTE in 12% of 455 patients with acute leukaemia, half of which occurred in association with central venous catheters, with equal risk of ALL and AML.

Increased risk of thromboembolism in patients with malignant lymphoma: a single-centre analysis.

An increased risk for thromboembolism in cancer patients has been observed in patients with solid tumours, whereas little data exist on malignant lymphoma. We found an overall thromboembolic event incidence of 7.7% in 1038 lymphoma patients treated in our institution, with a statistically significantly higher incidence in high-grade than in low-grade lymphoma.

[Case report. Phenprocoumon (Marcumar, Falithrom) as an unusual reason for coumarin poisoning in a dog]. / Phenprocoumon (Marcumar, Falithrom) als ungewöhnliche Ursache einer Kumarinvergiftung beim Hund.

Coumarin poisoning in dogs is not unusual and is in most cases caused by warfarin, a coumarin derivative which is used as a rodenticide. Competitive inhibition of vitamin K with an incomplete synthesis of the coagulation factors II, VII, IX and X can lead to a significant bleeding tendency. We observed a 3-year old male West Highland White Terrier with a reduced general condition and dyspnoea together with a massive haemothorax. Administration of vitamin K1 (3 mg/kg) led to a rapid improvement of the condition. Coagulation analysis revealed a prolonged activated recalcification time (ARCT), prothrombin time (PT) and aPTT with uncharacteristic thrombin time (TT); factor II, VII and X activities were reduced while factor V activity was normal, all of which are characteristic for coumarin poisoning. HPLC did not reveal the presence of warfarin but of phenoprocoumon, a drug used for thromboembolic prophylaxis in humans. This observation has not been described for dogs to date.

Platelet concentrates derived from buffy coat and apheresis: biochemical and functional differences.

Today, platelet concentrates are generally produced from whole blood by differential centrifugation (buffy coat-derived platelet concentrates--PCs) or by plateletpheresis (apheresis-derived platelet concentrates--APCs). As PCs are characterized by a lower number of platelets than APCs, four to six PCs are customarily combined in order to obtain an equivalent dose. In the 1970s and 1980s, the use of PCs exceeded that of APCs by far; in contrast, since the beginning of the 1990s, APCs comprise more than half of all transfused platelets. However, the selection of PCs or APCs for transfusion to thrombocytopenic patients is still a matter of debate. The present paper compares biochemical and functional properties of both platelet preparations in vitro. Besides plasma parameters (e.g. platelet factor 4 (PF4), P-selectin, C3a-desarginin, plasma coagulation factors), platelet function was analysed by aggregometry and the PFA 100 system. APCs are characterized by a better preservation of ADP and collagen-induced platelet aggregation, and shorter closure times of the PFA 100 test system during storage. The improved primary in vitro haemostatic capacity of APCs is presumed to be owing to a lower cellular activation rate in these preparations. This hypothesis is supported by the higher plasma concentrations of PF4, beta-thromboglobulin and P-selectin found in PCs compared with APCs. The concentrations of C3a-desarginin in PCs exceed those in APCs by far. Additionally, thrombin generation is higher in PCs than in APCs. These data suggest that APCs are characterized by a superior haemostatic capacity over PCs in vitro. However, in vivo studies should be performed to confirm these findings in the patients' circulation also.

[Postoperative haemorrhagia in a girl with congenital factor XI deficiency - successful treatment with desmopressin (DDAVP, Minirin(R))]. / Postoperative Blutung bei einem Mädchen mit angeborenem Faktor-XI-Mangel - erfolgreiche Therapie mit Desmopressin (DDAVP, Minirin(R)).

UNLABELLED: The rare factor XI deficiency is associated with different profuse bleeding without correlation to the severity of reduction of factor XI. Accordingly, traumata or surgical procedures may cause unexpected excessive bleeding in asymptomatic patients. After surgery of a nine-year-old girl with factor XI deficiency (8 per cent) profuse bleeding occurred which could only be stopped after infusion of desmopressin. After administration the factor XI activity was increased to 31 per cent, the factor VIII even to 290 per cent over the normal range. We suppose that the favorable clinical effectiveness is not only related to the increasing factor XI activity but also to the elevation of the factor VIII/von-Willebrand-complex. CONCLUSION: It is recommended to give desmopressin as firstline therapy of bleeding by factor XI deficiency since the only effective alternative such as substitution of factor XI by transfusion of fresh frozen plasma is associated with the risk of transmission of virus infections.

[Factor VIII inhibitors in patients suffering from severe haemophilia A: problems of "very low" responders]. / Faktor VIII-Inhibitoren bei Patienten mit schwerer Hämophilie A: Problematik der "very low" Responder.

Without recognition of any inhibitor until now, low concentrations of factor VIII inhibitors (< 1 Bethesda unit (BU)/mL plasma) can be occasionally measured in patients with severe haemophilia A. The existence of so-called "very low" responders is assessed contradictorily due to a methodically caused inhibitor increase. Plasma from 10 patients with severe haemophilia A was incubated with human plasma or animal plasma from pig, cattle, or cat and assayed for factor VIII inhibitors. No signs of inactivation could be detected in five specimen (0 BU/mL plasma). However, measurable signs of factor VIII inactivation (< 1 BU/mL plasma) did occur in the other five. Therefore, the existence of yet not defined unknown inhibitory substances in certain haemophilic plasmas must be assumed. They are directed against human factor VIII as well as partly against animal factor VIII. These "very low" inhibitors are not identical with factor VIII antibodies of "low" and "high" responding haemophiliacs. The clinical importance of "very low" inhibitors is insignificant because they do not tend to increase after exposure to factor VIII. In fact, a effect of factor VIII therapy is the neutralization of this kind of inhibitors.

Acetylsalicylic acid and microembolic events detected by transcranial Doppler in symptomatic arterial stenoses.

BACKGROUND: In patients with symptomatic carotid artery stenosis, high-intensity transient signals detected by transcranial Doppler (TCD) have been related to particulate microemboli originating at the stenotic lesion. The occurrence of these microembolic events within the Doppler spectrum should be influenced by antithrombotic agents of proven efficacy in these patients mainly by reducing cerebral embolism. METHODS: Seventy-four of 192 consecutive patients with symptomatic arterial stenosis in the anterior circulation and clinical symptoms within the last 30 days underwent 1-hour bilateral TCD monitoring. Patients were selected, if they presented temporal bone windows enabling transcranial insonation, revealed normal Doppler CO2 test excluding hemodynamic impairment, had not received antithrombotic therapy other than acetylsalicylic acid (ASA) before sonographic examination, and gave informed consent to 1-hour monitoring which could be performed immediately on admission/presentation of the patient at the Department of Neurology. RESULTS: Microembolic events were detected in 38 patients (51%). The proportion of patients with events among 26 patients without antithrombotic medication was 73% as compared with 40% in 48 patients receiving ASA at the time of TCD monitoring (p = 0.023). Multivariate analysis including time from ischemia to TCD, presence and start of ASA prevention, degree and localization of stenosis, and presence of a single or recurrent ischemia revealed that absence of an ASA prevention (odds ratio OR 7.1, 95% confidence interval CI 1.6-31.4, p = 0.010), recurrent ischemic events (OR 7.1, 95% CI 1.6-32.7, p = 0.011), and extracranial localization of the stenosis (OR 3.8, 95% CI 1.1-13.2, p = 0.038) were independent predictors for microembolic events. CONCLUSION: In patients with symptomatic arterial stenosis, the absence of an ASA medication is associated with the occurrence of TCD-detected microembolic events, suggesting a relation between these events and ASA-sensitive microemboli from the stenotic lesion.

Rapid decline of cerebral microemboli of arterial origin after intravenous acetylsalicylic acid.

BACKGROUND AND PURPOSE: The present study investigated the influence of the antiplatelet agent acetylsalicylic acid (ASA) on cerebral microembolism as detected by transcranial Doppler sonography (TCD). METHODS: Nine patients with recent transient ischemic attack or minor stroke of arterial origin were investigated. Eight had not received an antiplatelet or anticoagulant medication before TCD, and in 1 patient a preexisting ASA medication (100 mg/d) had not been changed since the onset of stroke symptoms. An initial 1-hour TCD monitoring was extended for an additional 2.5 hours after an intravenous bolus injection of 500 mg ASA and was repeated for 1 hour on the following day. RESULTS: Microembolic signals (MES) were detected in all patients only on the symptomatic side. After the ASA bolus injection, a significant drop of the MES rate was found in 7 patients, all without previous medication, starting 30 minutes after the application (mean per hour=25.1 [range, 6 to 66] versus mean per hour=6.4 [range, 0 to 14]). In 3 of these patients, platelet aggregation tests were performed that demonstrated normal aggregation before bolus injection and inhibited aggregability as early as 30 minutes after bolus injection. The rate of MES remained unchanged in 1 patient without antiplatelet medication. The ninth patient, who had suffered an ischemic event on ASA, showed only a transient decrease of MES frequency. CONCLUSIONS: In patients with recent stroke of arterial origin, intravenous ASA can rapidly reduce cerebral microemboli as detected by TCD. Microemboli might be a useful parameter to monitor early effects of antiplatelet therapy.

Mutations in the human factor XII gene.

The factor XII gene from 31 unrelated factor XII-deficient patients from Germany, Switzerland, and Austria was screened for mutations at the genomic level. Several novel mutations were detected and their absence in a control group of 74 healthy unrelated individuals was checked. Most changes are in the serine protease domain affecting the catalytic triad His-393-Asp-442-Ser-544; two missense mutations, R398Q (arginine 398 to glutamine; gene bank accession no. U71276) and L395M (leucine 395 to methionine; gene bank accession no. U71277), are close to the active site histidine at position 393. Another mutation detected in a cross-reacting material (CRM)-positive female with a history of three abortions affects the active site aspartic acid by changing it to asparagine (D442N; gene bank accession no. U71275). The novel mutation G570R (glycine 570 to arginine; gene bank accession no. U71274) giving rise to a CRM-positive phenotype is located next to Cys571, which forms a vital disulfide bridge. Two mutations are causing reading frame shifts: one single basepair deletion in exon 12 [exon 12: 10590(DelC); gene bank accession no. U71278] and one acceptor splice site mutation [exon 14: 11397(G --> A); gene bank accession no. L43615]. The putative regulatory mutation exon 1:-8 (g --> c) in the upstream region of the gene is associated with an aberrant Taq I restriction site allele in intron B of the gene (gene bank accession no. X80393).

Multicenter evaluation of a new capillary blood prothrombin time monitoring system.

The analytical performance of the new capillary blood prothrombin time monitoring system CoaguChek was examined in a multicenter evaluation at six hospitals. The coefficients of variation of the INR obtained in the CoaguChek imprecision study were approximately 7% in the control plasma provided (within-run and day-to-day) and 4% in blood (within-run). The prothrombin times were ascertained in capillary blood (CoaguChek PT Test) and citrated venous plasma (Hepato Quick, Thromborel S) from 359 patients under oral anticoagulation therapy with phenprocoumon, acenocoumarin or warfarin. The agreement with the test results obtained with the comparison methods was acceptable versus Hepato Quick assay (n = 359; y = 1.23 x -0.49, r = 0.888) and good versus Thromborel S method (n = 359; y = 1.09 x -0.28, r = 0.895). A simplified assessment of all test results (n = 795) in a nine-field comparison table showed a concordance with the comparison methods of more than 80 (Hepato Quick: 81%, Thromborel S: 83%). The concordance between Hepato-Quick and Thromborel S was slightly higher (88%). Its good analytical performance and convenient handling recommend the CoaguChek system as a suitable system for decentralized prothrombin time testing.

[Severe acquired protein S deficiency with thrombophlebitis after febrile infection in a 7-year-old girl]. / Schwerer erworbener Protein S-Mangel mit Beinvenenthrombose nach fieberhaftem Infekt bei einem 7jährigen Mdchen.

The importance of the anticoagulant properties of protein S is illustrated by the high incidence of thromboembolic events in individuals with protein S-deficiency. A 7 year old girl was hospitalized with purpura-like bruises and lesions on both thighs after she had suffered from febrile infection. A subsequently developing thrombosis of the left V. femoralis was treated successfully with urokinase. Haemostaseological investigations showed no signs of disseminated intravascular coagulation. However, isolated severe degradation or all protein S-components due to the presence of a circulating autoantibody to protein S was found. After several months the antibody was detectable not any more, activity and antigens of protein S were normal.

[Activity and concentration determinations of coagulation factors in conventional and virus-inactivated coagulation-active plasma]. / Aktivitäts- und Konzentrationsbestimmungen von Gerinnungsfaktoren in konventionellen und virusinaktivierten gerinnungsaktiven Plasmen.

Deep-frozen conventional plasma without viral inactivation [fresh frozen plasma (FFP)] and virus-inactivated plasma units [solvent/detergent (SD) procedure, methylene blue/illumination (MB) procedure] were investigated with regard to their contents of particles and their activities and concentrations, respectively, of blood clotting factors. Particles could be proved in FFP and in MB-treated plasma, but not in SD-treated plasma. Results of the global tests prothrombin time, partial thromboplastin time and thrombin time as well as the activities of blood clotting factors were located in normal range in SD-treated plasma. However, pathological results were partly found in MB-treated plasma. Activities of protein S and alpha 2-antiplasmin were lessened in SD-treated plasma. FFP and MB-treated plasma showed interindividual variations of outcomes (single-donor plasma units) in contrast to SD-treated plasma (pooled donor plasma units).

[Determination of the activity of single coagulation factors in clinically healthy swine and cattle]. / Aktivitätsbestimmungen von Einzelfaktoren der Gerinnung bei klinisch gesunden Schweinen und Rindern.

Special details of animal haemostaseological investigations are insufficiently known as yet. This concerns as well the use of standardized laboratory methods as the differences between species and the normal ranges. Global tests and determinations of activity of single blood clotting factors (II, V, VII - XII, AT III) were carried out on healthy pigs and cattle. Quantitative evaluations were performed by using human or animal reference plasmas. Special attention was paid to the determinations of single blood clotting factors.

[Kinetic fibrinogen determination with batroxobin (reptilase)]. / Kinetische Fibrinogenbestimmung mit Batroxobin (Reptilase).

A kinetic turbidity-producing method for fibrinogen determination on the basis of reptilase reagent (batroxobin) is described. The method, which is in good agreement with method by Clauss shows comparable precision, is marked out by the possibility of objective photometric measurement. Reagent stability, use of undiluted test plasma and single-point calibration are further advantages. The method is insensitive to heparin. With regards to FDP it is less disturbed than the method by Clauss. In case of adaptation to a modern photometer a clear rationalization effect can be achieved.

[The plasma coagulation system of domestic cats]. / Untersuchungen zum plasmatischen Gerinnungssystem der Hauskatze.

Haemostaseological investigations of the animals need improvement. Usual methods in human medicine have to be reconsidered with regard to their qualification for veterinary medicine. A standardization of methods and accurate haemostaseological characterization of the reagents used are necessary for an appropriate interpretation of the results and interlaboratory comparative studies. Results of global tests (ARZ, PTT, TZW, TZ, RZ) and determinations of activity of single blood clotting factors (I, II, V, VII-XII) in healthy cats are presented and discussed in view of the mentioned.