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PubMed1994

Multicentric evaluation of a new PT reagent based on recombinant human tissue factor and synthetic phospholipids.

A new PT reagent based on recombinant human tissue factor and synthetic phospholipids (phosphatidyl choline and phosphatidyl serine) with defined fatty acid side chains was calibrated against BCT/253 and CRM 149R. A small but consistent bias in the International Sensitivity Index (ISI) value was obtained using either the human or rabbit brain reference material. ISI values were around 1.0 or slightly lower depending on the respective instrument. Mixing studies with factor deficient plasmas showed a high factor sensitivity especially for factor VII as compared to commercial rabbit brain or human placenta thromboplastin. In an international field trial the reagent was tested using fully or semi automated Electra coagulometers in 4 different laboratories. Results with normal samples were in excellent agreement among the different laboratories. Mean values were 10.9, 10.9, 11.0, 11.2 s with a range of 9.5 to 12.5 s. Results of males and females were not different. In patients with liver disease very similar PT activities were found as compared to sensitive rabbit brain or human placental thromboplastins. In normals and patients with oral anticoagulation INR values correlated very well against BCT (r = 0.98, regression line y = -0.07 + 0.9 x). The distribution of samples was linear over the whole range. In the comparison against sensitive rabbit brain thromboplastin or human placental thromboplastin similar correlations were found. In a few cases higher INR values were observed for the recombinant reagent especially in patients with intensive treatment. Factor assays in those patients showed at least the strong reduction of one vitamin K-dependent coagulation factor.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Drawing coagulation studies from arterial lines: an integrative literature review.

How much blood must be discarded from a heparinized arterial line to obtain accurate coagulation studies, specifically activated partial thromboplastin time? The published literature provides insight into the question and guidelines for practice in adult critical care. This article reviews and integrates findings from 14 research studies published from 1971 to 1993 on discarding blood from arterial lines for coagulation studies. Investigators compared activated partial thromboplastin time values from arterial and venous blood samples using various discard volumes, sites and sizes of catheters, and heparin flush concentrations. Similarities and differences in arterial and venous activated partial thromboplastin time were reported. Studies have demonstrated that adequate discard volume for activated partial thromboplastin time is 6 times the catheter dead space. These results should not be generalized to systemically heparinized patients, pediatric patients, or other types of heparinized lines such as pulmonary artery, central venous, or Hickman catheters.

Blood Specimen Collection↗

PubMed1976

[Laboratory standardization and quality control in anticoagulant therapy].

Standardisation and quality control are now available for the laboratory tests which are needed to control the blood levels of anticoagulants. The most important cause for variation in results between different laboratories is the use of different types of thromboplastin. The British standards are based on the use of a national reagent with a national system of reporting supported by quality control with lyophilised plasma and thromboplastin preparations. It offers a model which has been adopted at Tygerberg Hospital, and could be used to standardise anticoagulant therapy in this country. Human brain thromboplastin is preferred to the commercially available rabbit preparations. For the first time, as far as we know, a phenol-saline extract of baboon brain thromboplastin was examined. Preliminary results indicate that it compares well with human brain extracts.

Animals↗

PubMed1996

Potential failure of the International Normalized Ratio (INR) System in the monitoring of oral anticoagulation in patients with lupus anticoagulants.

Patients with antiphospholipid antibody syndrome (APS) experience a higher rate of recurrence of thrombosis than the general population of patients with thrombotic disease. Based on a retrospective analysis, it has been suggested that patients with APS should be kept on prolonged anticoagulation aiming at international normalised ratio (INR) values > 3.0. To evaluate whether the requirement for more intense anticoagulation depends on the variable sensitivity of thromboplastin reagents to the influence of aPLA, we monitored oral anticoagulant treatment in 10 patients with persistent lupus anticoagulants (LA) and venous thromboembolic disease using two thromboplastin reagents: Pro-IL-Complex (Instrumentation Laboratory, combined) and Recombiplastin (Ortho, recombinant). Acenocoumarol dosage was always assigned based on INR values obtained with the combined thromboplastin using diluted (1:20) test plasma, aiming at an INR interval of 2.0 to 3.0. Single INR determinations with both reagents were obtained throughout the study period for 110 aPLA-free patients on stable oral anticoagulation. Using the manufacturer's instrument-certified international sensitivity index (ISI) values, INR obtained with the recombinant reagent were significantly higher than those obtained with the combined reagent in LA-positive patients, but they were lower in LA-negative patients. After correction for local ISI calibration in LA-negative patients, INR values of 3.1 and 4.6 with Recombiplastin corresponded, respectively, to INR values of 2.0 and 3.0 with Pro-IL-Complex. These results indicate the thromboplastin-dependency of INR values in patients with LA, thereby questioning the validity of the INR system for the monitoring of oral anticoagulant treatment in these patients.

Administration, Oral↗

PubMed2000

Clinical utilization of the international normalized ratio (INR).

The prothrombin time (PT) is one of the most important laboratory tests to determine the functionality of the blood coagulation system. It is used in patient care to diagnose diseases of coagulation, assess the risk of bleeding in patients undergoing operative procedures, monitor patients being treated with oral anticoagulant (coumadin) therapy, and evaluate liver function. The PT is performed by measuring the clotting time of platelet-poor plasma after the addition of calcium and thromboplastin, a combination of tissue factor and phospholipid. Intra- and interlaboratory variation in the PT was a significant problem for clinical laboratories in the past, when crude extracts of rabbit brain or human placenta were the only source of thromboplastin. The international normalized ratio (INR), developed by the World Health Organization in the early 1980s, is designed to eliminate problems in oral anticoagulant therapy caused by variability in the sensitivity of different commercial sources and different lots of thromboplastin to blood coagulation factor VII. The INR is used worldwide by most laboratories performing oral anticoagulation monitoring, and is routinely incorporated into dosage planning for patients receiving warfarin. Although the recent availability of sensitive PT reagents prepared from recombinant human tissue factor (rHTF) and synthetic phospholipids eliminated many of the earlier problems associated with the use of crude thromboplastin preparations, local instrument variability in the INR still remains a problem. Presently, the use of plasma calibrants seems the best solution to this problem. Standardizing the point-of-care instruments for INR monitoring is another dilemma faced by the industry. Ultimately, new generations of anticoagulant drugs may eliminate the need for laboratory monitoring of anticoagulant therapy.

Hematology↗

PubMed1985

Lupus anticoagulant: an analysis of the clinical and laboratory features of 219 cases.

To define clinical and laboratory characteristics of the lupus anticoagulant (LA), we reviewed our experience (219 subjects). Subjects were divided into group A, those with the LA and the diagnosis of lupus erythematosus, group B, those with the LA but nonlupus diagnoses, and group C, those with drug-related lupus syndromes. The typical laboratory findings consisted of a prolonged and inhibited plasma clot time (an average of 1.9 times control time) which was proportionately more prolonged than the partial thromboplastin time or activated partial thromboplastin time (APTT) (average 1.3 times control). Ninety-eight percent had a prolonged plasma clot time and 94% had a prolonged partial thromboplastin time. The prothrombin and thrombin times were prolonged in 33 and 25% of subjects, respectively. Washed platelets shortened the APTT in the 22 subjects so tested. Monoclonal protein peaks were seen in 7% of patients. Seventeen episodes of bleeding were observed, but in all but one instance there was another hemostatic defect present. In the 18 patients who underwent major operations, there were no hemorrhagic complications. Fifty-eight episodes of thrombosis were observed with the same incidence in group A (25%) as in group B (26%). Bleeding is rare with the LA but thrombosis is common even without SLE and lupuslike syndromes. The plasma clot time in platelet-rich plasma is more prolonged, and in our experience, is more sensitive in detecting the lupus anticoagulant than is the partial thromboplastin time.

Abortion, Spontaneous↗

PubMed1989

Does nitroglycerin induce heparin resistance?

We studied the possibility that intravenous nitroglycerin may produce heparin resistance both in vitro and prospectively in a group of 10 patients following coronary angioplasty. Nitroglycerin in physiologic to pharmacologic concentrations (41-250 micrograms/ml) did not produce heparin resistance in vitro as measured by activated partial thromboplastin time and thrombin time. The maximum reduction in activated partial thromboplastin time was 7%. In patient studies, the activated partial thromboplastin time at baseline on heparin alone (93 + 22 s) was not significantly different (p = 0.61) from activated partial thromboplastin measured upon addition of nitroglycerin (94 +/- 27 s) or 30 min following cessation of the nitroglycerin infusion while continuing the same dose of heparin (91 +/- 24 s). We conclude that intravenous nitroglycerin does not induce heparin resistance in vitro or in patients during short-term administration.

Angioplasty, Balloon↗

PubMed1996

Anticoagulant activity of Triatoma infestans and Panstrongylus megistus saliva (Hemiptera/Triatominae).

Salivary gland extract of Triatoma infestans prolonged thrombin time, prothrombin time, and activated partial thromboplastin time, while salivary gland extract of Panstrongylus megistus delayed thrombin time and activated partial thromboplastin time. However, saliva of P. megistus prolonged activated partial thromboplastin time and saliva of T. infestans delayed activated partial thromboplastin time and prothrombin time. T. infestans saliva interferes particularly with activity of factor VIII (intrinsic pathway) and factor V (common pathway), but also affects other factors. Saliva of the triatomine species studied presented distinct SDS-PAGE profiles. These results demonstrate that there are differences in anticoagulant activity and protein composition of triatomine saliva.

Animals↗

PubMed1985

Studies on the procoagulant activity of human amniotic fluid. II. The role of factor VII.

Partially purified Amniotic Fluid Factor (AFF) is found to directly activate human factor X, with a Km for factor X of 0.37 +/- 0.06 M. Added phospholipid has only a slight effect on the activation at low concentrations, and inhibits the reaction at higher concentrations. Both DIPF and PMSF inhibit AFF factor X activation. Although added phospholipid is not required for AFF-activity, phospholipase C rapidly destroys it, indicating the presence of intrinsic phospholipid. Phospholipase C treated AFF releases factor VII activity, which leads to the conclusion that AFF is in fact a thromboplastin: factor VII complex. Both AFF and a human brain thromboplastin factor VII complex prepared in vitro were inhibited by Zn++ ion, while human brain thromboplastin alone is not. AFF is markedly larger than the human brain thromboplastin-factor VII complex as judged by gel filtration.

Amniotic Fluid↗

PubMed1992

Prognostic value of hemostatic parameters after liver transplantation.

The prognostic value of hemostatic parameters after orthotopic liver transplantation was evaluated in 37 consecutive patients. Six simple hemostatic parameters (prothrombin time, activated partial thromboplastin time, thrombin time, thrombin coagulase time, plasma fibrinogen and platelet count) were obtained for each patient pre-transplantation and daily post-transplantation for at least 8 days. Using the results of these tests, the degree of hemostatic impairment was arbitrarily scored from 0 to 6. Starting from the first day post-transplantation, hemostatic parameters improved progressively, reaching plateau values on day 7 post-transplantation. On day 8 there were significant differences in the activated partial thromboplastin time, prothrombin time, and in the overall hemostatic scores between patients who survived at least 6 months and those who died. Comparing these hemostasis parameters with such liver function tests as AST, ALT and serum bilirubin, univariate analysis showed that activated partial thromboplastin time, coagulation score and AST were significant predictors of 6-month survival, but by multivariate analysis (Cox proportional hazard rate model) only the activated partial thromboplastin time was an independent predictor. Hence, a simple coagulation test is useful for predicting the survival of patients undergoing liver transplantation.

Adolescent↗

PubMed1997

Monitoring of oral anticoagulant therapy in lupus anticoagulant positive patients with the anti-phospholipid syndrome.

Introduction of the International Normalized Ratio (INR) has improved the standardization of laboratory control of oral anticoagulant therapy (OAT). However, it has been reported that misleading INR results can be obtained from OAT patients with lupus anticoagulant (LA). To investigate this claim, we studied 35 OAT patients, 14 of whom had anti-phospholipid syndrome (APS) with a documented LA. Attainment of anticoagulation was confirmed by chromogenic assay of factor VII and factor X. Prothrombin times were performed using eight thromboplastins (five derived from rabbit brain, two recombinant human tissue factor and one made from human placenta) with an International Sensitivity Index (ISI) of <1.40. When using the thromboplastin manufacturers' ISI there was a significant difference (ANOVA, P<0.0001) between INR results obtained with the eight reagents for both APS (average CV = 12.4%) and non-APS (average CV = 12.5%) patient groups. Variation using the eight thromboplastins was assessed by calculating the CV for each sample; these values were then pooled for each patient group to give the average CV for all samples with all reagents for the two patient groups. Results for both patient groups exhibited markedly reduced variation (APS group average CV = 6.5%, non-APS group average CV = 5.8%) when locally assigned ISI values were employed in the calculation of INRs. Our data does not support the suggestion that the INR may not reflect the true level of anticoagulation in the long-term warfarin-treated patient, in whom lupus anticoagulant was detected. However, there was strong evidence that thromboplastin use should be restricted to those clot detection systems for which the reagent's manufacturer has assigned an ISI, or local ISI assignment must be undertaken. The inappropriate use of a generic (i.e. optical or mechanical clot detection system without regard to specific analyser type) ISI value can lead to ambiguous results.

Adult↗

PubMed2001

[Laparoscopic splenectomy in thrombotic thrombocytopenic purpura. Surgical and hematological results in 2 patients].

HISTORY: Case 1. Thrombotic-thrombocytopenic purpura (TTP, Moschkowitz' disease) in a 57-year-old woman had for one year been treated conservatively. But when daily plasmapheresis was temporarily discontinued she developed behavioural changes and impaired speech, providing an indication for splenectomy. Case 2. A 53-year-old woman with TTP had been similarly treated for one month. Splenectomy was indicated when neurological symptoms rapidly developed. INVESTIGATIONS: At admission, creatinine 110 mg/d, white cell count (WBC) 12.4 G/l haemoglobin 10.1 g/dl, haematocrit 0.29, platelets 91 G/l. Prothrombin time (PTT) and thromboplastin time were normal. Patient 2. At admission, platelet count was below 10 G/l and she had various neurological abnormalities. Haemoglobin was 9.0 f/dl, haematocrit 0.27. Platelet count, PTT, thromboplastin time and renal functions were normal. TREATMENT AND COURSE: Case 1. After plasmapheresis and administration of cryoprecipitate-free fresh frozen plasma (FFP) excess, laparoscopic splenectomy was performed. On the third postoperative day WBC count was 11.5 G/l, haemoglobin level was unchanged, but platelet count was now normal, as were PTT and thromboplastin time and renal functions. 8 and 32 months after the operation WBC count, haemoglobin, haematocrit and platelets were all normal. There were no neurological abnormalities postoperatively. Case 2. Laparoscopic splenectomy was performed after intensive haematological preparation. The pre- and postoperative course was uneventful and she was discharged on the 8th postoperative day, at which time her haemoglobin was 8.4 g/dl, haematocrit 0.25, while platelets, PTT, thromboplastin time and renal functions were all normal and remained so at follow-up 11 months later. There have been no neurological symptoms after the splenectomy. CONCLUSION: Laparoscopic splenectomy is a haematologically and surgically safe treatment of TTP and should be considered for all cases of TTP that fail to respond to conservative management.

Female↗

PubMed2000

Another method to prevent venous thrombosis in microsurgery: an in situ venous catheter.

Free-flap failure is in the order of 4 to 10 percent. Heparin is more effective at preventing venous thrombosis than arterial thrombosis. This study was undertaken to investigate the efficacy of delivering heparin at a high dose locally but low dose systemically (heparin infusion via a catheter placed proximal to the venous anastomosis) to prevent venous thrombosis in microsurgery. A model of venous thrombosis was first established by a venous inversion graft in the rat femoral vein (this was performed in seven animals and resulted in 100 percent thrombosis). Saline and heparin were delivered proximal to the inverted vein graft to assess the effect of each in preventing venous thrombosis. Flow/patency distal to the inverted vein graft was assessed by observation under the microscope, the milk test, and rate of flow (flowmeter). Saline infused via a catheter proximal to the venous inversion graft resulted in 100 percent thrombosis in 10 animals. Heparin (100 U/ml at 2 to 3 ml/hour) infused through a catheter for 2 hours proximal to the anastomosis resulted in flow in all 10 animals during the infusion. Blood was also taken before beginning the procedure (control) and after the heparin infusion distal to the anastomosis (local partial thromboplastin time) as well as in the contralateral femoral vein (systemic). The control for all animals that received heparin was <3 minutes. The systemic partial thromboplastin time after heparin infusion was <3 minutes in seven animals, 3.3 minutes in two animals, and >7 minutes in one animal. The local partial thromboplastin time distal to the inverted vein graft was >10 minutes in nine animals and 3.7 minutes in one animal. The study also had a clinical component, in which a catheter was placed in a vein of the free flap, and heparin was infused over 5 days. This technique has been used in 83 consecutive free flaps. In three recent free flaps performed on the limbs, the local partial thromboplastin time (close to the anastomosis) was raised but the systemic time was normal. This technique offers a method in preventing venous thrombosis in microsurgery. It is simple to implement and is not associated with the systemic complications of heparin.

Adult↗

PubMed1988

Factor VII activity and antigen in a patient with abnormal factor VII.

A patient with abnormal factor VII, which showed different activity when thromboplastin from different sources was used, is reported. The propositus, who was first seen at routine health examination 1 month after delivery, was a girl with no complaints of bleeding. The coagulation pattern was characterized by an abnormal clotting time using Normotest reagent which did not respond to the administration of vitamin K. Factor VII activity was decreased when measured using rabbit brain and lung thromboplastin, mildly decreased using human brain or human placenta thromboplastin and within the normal range using ox brain thromboplastin. The level of factor VII antigen was normal and revealed a normal mobility on immunoelectrophoresis. The molecular weight of this factor VII was not different from normal factor VII when analysed using autoradiography after sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). It seems probable that the propositus had an abnormality similar to the factor VII Padua 1 described previously.

Antigens↗

PubMed1977

An immunological investigation of hemophilia B with a tentative classification of the disease into five variants.

23 patients with hemophilia B have been investigated by means of several immunological methods. 16 patients (69.9%) had no detectable factor XI antigen. Five had a normal factor IX antigen and the electrophoretic mobility of this abnormal factor IX was similar to that of its normal counterpart. One of these five patients had hemophilia Bm, since ox brain thromboplastin clotting time was severely prolonged. The remaining two patients had reduced or decreased factor IX antigen. Several patients showed a slight protongation of ox brain thromboplastin time due to an associated slight factor VII deficiency. On the basis of these results, a tentative classification of hemophilia B into five variants is proposed, namely: hemctor IX antigen; hemophilia Bra, or with reduced factor IX antigen; hemophilia Bm, or with normal factor IX antigen and severely prolonged ox brain thromboplastin; hemophilia B patients is feasible only by means of a battery of tests, namely:factor IX activity assay, factor IX antigen determination, ox brain thromboplastin clotting time, factor VII activity assay.

Factor IX↗

PubMed2005

Effectiveness of a computerized system for intravenous heparin administration: using information technology to improve patient care and patient safety.

To overcome errors in prescribing, calculating doses, and monitoring intravenous heparin, a computerized heparin nomogram system (HepCare) was developed to improve heparin safety using interactive cues between the prescriber, nurse, pharmacist, and the laboratory. The frequency of deviations decreased from 0.5 per patient before HepCare with the protocol to 0.006 per patient with HepCare and the protocol. The goal activated partial thromboplastin time results of the HepCare system (group I) were compared with patients who were not treated using the HepCare system (group II). There was a higher mean percentage of activated partial thromboplastin times within goal range in group I vs. II-44% vs. 27% (p<0.01). There were reminders of a drop in platelet count in 6% of patients, hemoglobin drop in 0.7%, and validation activated partial thromboplastin time values in 7% of patients by HepCare. HepCare-guided intravenous heparin resulted in significant improvements in safety, quality assurance, and targeted activated partial thromboplastin time values.

Anticoagulants↗

PubMed1998

Prothrombin time derived fibrinogen determination on Sysmex CA-6000.

AIM: To evaluate PT derived fibrinogen determinations with reference to the Clauss fibrinogen assay using a Sysmex CA-6000 random access coagulation analyser. METHODS: Samples were analysed from normal subjects (n = 20), patients with renal or liver dysfunction (n = 25), critically ill patients (n = 25), patients receiving oral anticoagulant treatment (n = 50), and patients with a haemoglobinopathy (n = 127). Prothrombin times were performed using two thromboplastins: one derived from rabbit brain (Dade: Thromboplastin IS) and the other from recombinant human tissue factor (Dade: Innovin). Fibrinogen was assayed by the Clauss method using a commercial kit (Dade: Fibrinogen). RESULTS: The relation between Clauss fibrinogen and PT derived fibrinogen was found to be dependent on the patient's clinical group and source of the thromboplastin used. When the data from the above sample groups were pooled there was still a significant difference (p < 0.001) between Clauss fibrinogen and PT derived fibrinogen, irrespective of thromboplastin used. CONCLUSIONS: It is unsafe to use the PT derived fibrinogen for patient monitoring owing to non-uniform variability in response to clinical status and reagent employed; however, it may prove to be a useful screening test in a research environment for estimating fibrinogen levels among defined patient groups.

Animals↗

PubMedDate not supplied

Comparative study of a portable monitor for prothrombin time determination, Coaguchek, with three systems for control of oral anticoagulant treatment.

Self-testing of oral anticoagulation is a new possibility related to the development of portable capillary whole blood prothrombin time monitors. The aim of this study was to evaluate one of this monitors, Coaguchek, with respect to its comparability with our routine prothrombin time determination system, as well as with the reference manual technique and two thromboplastins of high sensitivity, Manchester Reagent and one manufactured in our center, Thromboplastin Bilbao, in a group of patients on oral anticoagulant treatment. Although a correlation of r = 0.9271 was found between international normalized ratio (INR) values of Coaguchek and our routine method, Neoplastine/STA analyzer, the difference of the INR scatter increased with the magnitude of measurement, being lowest for INR between the portable monitor and Manchester Reagent and Thromboplastin Bilbao, with a similar coefficient of correlation, r = 0.8948 and r = 0.8905, respectively. A test was performed showing a 65.6% agreement with the INR values of the STA analyzer, 66.4% with Manchester Reagent and 73.4% with Thromboplastin Bilbao. On the basis of this correspondence with laboratory prothrombin time results Coaguchek may be considered as a possible option for monitoring anticoagulated patients even though patients should be given instructions and advice as regards the management and interpretation of the results.

Administration, Oral↗