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PubMed1980

Kaolin-correctable prolongation of the activated partial thromboplastin time.

Seven patients who had normal prothrombin times but prolonged activated partial thromboplastin times (aPTT) are described. The prolonged aPTT, obtained with micronized silica as the contact activating agent in a semi-automated optical end-point system, a nonautomated optical end-point system, and a conductivity end-point system, corrected to normal when kaolin was used as the contact activating agent. Abnormal results were also obtained with celite and ellagic acid as contact activating agents. The activities of various clotting factors were within normal limits in all cases where they were assayed. The thromboplastin dilution test was uniformly negative, and mixtures of one patient's plasma with that of another patient failed to correct the abnormal aPTT. No patients had a personal or family history of bleeding, and all underwent surgery without bleeding difficulties. This pattern of a prolonged aPTT that corrects to normal when kaolin is used as the contact activator appears to represent a previously unrecognized laboratory phenomenon.

Adult↗
PubMed1986

Sensitivity of three activated partial thromboplastin time reagents to coagulation factor deficiencies.

Three activated partial thromboplastin time (APTT) reagent test systems, General Diagnostics Automated APTT, American Dade Actin FS, and Pacific Hemostasis (Thromboscreen KAPTT) reagent, containing different activators for the APTT assay, were evaluated for their precision and sensitivity to factor deficiencies in the intrinsic coagulation system. The data suggest that micronized silica and ellagic acid reagent systems were similar in sensitivity to Factor VIII, X, and XII deficiencies, whereas, the micronized kaolin reagent was significantly less sensitive to these deficiencies. Factor XI deficiency was detected equally well with the use of all three reagent systems. The ellagic acid reagent was somewhat more sensitive to Factor IX deficiency than the micronized silica reagent, and the micronized kaolin reagent was again least sensitive. Both the micronized silica and ellagic acid based reagents were insensitive to all but severe deficiencies in prekallikrein, whereas the micronized kaolin reagent was unable to detect this deficiency. All three reagents were insensitive to all but severe deficiencies in high-molecular-weight kininogen. The authors conclude that the reagent systems tested, containing micronized silica or ellagic acid as activators, are similar in sensitivity when used in a routine activated partial thromboplastin time to screen for factor deficiencies, whereas the reagent system containing micronized kaolin as an activator is less sensitive.

Adult↗
PubMed1986

The effect of calcium ions on the activated partial thromboplastin time of heparinized plasma.

The effect of calcium chloride (CaCl2) on the activated partial thromboplastin time (aPTT) of heparinized plasma was studied. The aPTT ratio (heparinized plasma:control plasma) increased as the CaCl2 concentration to recalcify the plasma was increased from 15 to 35 mmol/L CaCl2. Platelet-poor plasma from patients receiving intravenous heparin, and in vitro heparinized plasmas from either coumarinized patients or plasma depleted of the vitamin K-dependent factors, displayed the calcium-dependent increase in the aPTT ratio. The magnitude of the calcium-dependent change in the aPTT ratio was similar for the three partial thromboplastins studied. Heparinized blood collected in 3.2% and 3.8% citrate demonstrated the calcium-dependent increase in the aPTT ratio. The authors have also studied the effect of the divalent cations (Ca+2, Mg+2, Zn+2, and Sr+2) on the anti-Factor Xa activity of heparin to determine whether the calcium-dependent increase in the aPTT was due to an increase in the anti-Factor Xa activity. The anti-Factor Xa activity of heparin was measured using chromogenic substrate S-2251, purified Factor Xa, and excess antithrombin III. The anti-Factor Xa activity of heparinized plasma increased 2.4-2.8-fold as the divalent cation concentration was increased from 0-5 mmol/L. Similar results were obtained using purified bovine Factor Xa, antithrombin III, and heparin in the absence of plasma. These results suggest that divalent cations play an important role in modulating heparin's anticoagulant activity in vitro. In addition, the CaCl2 concentration used to recalcify plasma is an important variable that modifies heparin sensitivity of the aPTT. Furthermore, divalent cations play an important role in regulating the anti-Factor Xa activity of heparin in vitro.

Blood Coagulation Tests↗
PubMed2002

The detection of changes in heparin activity in the rabbit: a comparison of anti-xa activity, thrombelastography, activated partial thromboplastin time, and activated coagulation time.

UNLABELLED: Thrombelastography (TEG) has been used to detect both exogenous and endogenous circulating heparin activity in clinical and laboratory settings. Thus, in this study I sought to compare the sensitivity of TEG, activated partial thromboplastin time (aPTT), and activated coagulation time (ACT) values with changes in anti-Xa activity after small-dose heparin administration in rabbits. Conscious rabbits (n = 11) had blood obtained from ear arteries for hematological analyses after the administration of 0, 10, 20, and 30 U/kg of IV heparin. Anti-Xa activities after the administration of 0, 10, 20, and 30 U/kg of heparin were, respectively, 38 +/- 9 mU/mL, 74 +/- 15 mU/mL, 105 +/- 14 mU/mL, and 134 +/- 17 mU/mL; all values were significantly different from each other. TEG variables (R and alpha) significantly (P < 0.05) changed between 0, 10, and 20 U/kg heparin doses, but a difference between 20 and 30 U/kg could not be discerned secondary to loss of a detectable clot. The aPTT was significantly (P < 0.05) different between 0, 20, and 30 U/kg doses. ACT values were significantly different between the 0 U/kg heparin dose and all other doses; however, there were no significant differences between the 10, 20, and 30 U/kg heparin doses. Changes in anti-Xa activity were significantly linearly related to R (r = 0.81, P < 0.0001), alpha (r = -0.85, P < 0.0001), aPTT (r = 0.74, P < 0.0001), and ACT (r = 0.41, P = 0.005). In this model of small-dose heparin administration, TEG variables were more sensitive to changes in heparin activity than aPTT and ACT. IMPLICATIONS: Changes in thrombelastography (TEG) variables more sensitively reflect changes in circulating heparin activity than activated partial thromboplastin time (aPTT) and activated coagulation time (ACT) after small-dose heparin administration in rabbits. Thus, TEG may be more helpful than aPTT and ACT in the detection of heparin in both laboratory and clinical settings wherein heparin may play a role in coagulopathy.

Animals↗
PubMed1996

Sensitivity of the activated partial thromboplastin time, the dilute Russell's viper venom time, and the kaolin clotting time for the detection of the lupus anticoagulant: a direct comparison using plasma dilutions.

Increasing dilutions of lupus anticoagulant (LA) plasmas from twelve patients were used to directly compare the sensitivity of four tests for LA. The tests evaluated were the modified Bell and Alton activated partial thromboplastin time (APTT), an APTT using a commercially prepared partial thromboplastin (Platelin LS APTT), a modified dilute Russell's viper venom time (DRVVT), and a modified kaolin clotting time (KCT). LAs were detected in all twelve plasmas by each of three tests and eleven of twelve plasmas in a fourth test when undiluted patient plasma was used. Repeating the tests after diluting the LA plasmas with normal platelet-free plasma (PFP) showed that the KCT was the most sensitive test for LA, detecting eleven of twelve LAs at a dilution of 10% patient plasma and ten of twelve LAs at a dilution of 5% patient plasma. The modified Bell and Alton APTT and the modified DRVVT had similar sensitivities at a patient plasma concentration of 10%, detecting seven of twelve and eight of twelve LAs, respectively. The Platelin LS APTT detected only four of twelve LAs at a patient plasma concentration of 10%. Our results indicate that the modified KCT is a sensitive method for the detection of LAs. The modified Bell and Alton APTT and the DRVVT were less sensitive.

Humans↗
PubMed1999

A study of the variability seen in the international normalized ratio obtained using different sensitivity thromboplastin reagents on different instrument types.

We performed an extensive study to check international normalized ratio (INR) recovery using three different rabbit thromboplastin reagents of different sensitivities [international sensitivity index (ISI) circa 1.1, 1.3 and 2.0] on two different instrument types. Both instrument types used an optical end point: one nephelometric at 660 nm, one photometric at 880 nm. Each thromboplastin reagent in the study had an instrument-specific ISI value assigned to it by the reagent manufacturer. Samples obtained from stable orally anticoagulated patients were tested on four different instruments of each type with the three different sensitivity reagents. Excellent correlation between INR values was seen between all results (r values between 0.97 and 0.99). Regression analysis gave slopes between 0.92 and 1.07, and a maximum deviation of intercept from zero of 0.21. Variations in CV of less than 2% were seen within each instrument type. This study shows that if instrument-specific ISI values are used, comparable INR values can be obtained using reagents of different sensitivity on multiple instruments of the same or different types. This study demonstrates the validity of the INR/ISI system.

Adult↗
PubMed1994

Optimization of the dilute prothrombin time for the detection of the lupus anticoagulant by use of a recombinant tissue thromboplastin.

The dilute prothrombin time (dPT) is a widely accepted sensitive screening test for the lupus anticoagulant (LA). In general, Simplastin (Organon Teknika), a rabbit brain thromboplastin, diluted 1/500, is used in this test. Recently, human tissue thromboplastin obtained by recombinant DNA technology has become available and we have evaluated the usefulness of one such preparation, Innovin (Dade), for the detection of the LA. dPTs, using several dilutions of Innovin were determined on plasmas from 18 normal individuals and 15 patients with a well-documented LA. The dPT ratios, calculated as the individual result divided by the mean normal, were statistically compared. Innovin in dilutions from 1/100 onwards was found to be significantly more responsive to the LA than Simplastin (P < 0.05). Intra-assay coefficients of variation (CVs) ranged from 1.05% to 14.8% with Innovin, versus 2.7%-24.3% with Simplastin (P < 0.05); inter-assay CVs ranged from 5.6%-11.8% with Innovin, versus 4.2%-33.8% with Simplastin (P < 0.001). Analysis of 316 consecutive plasma samples from non-anticoagulated patients, on which a LA determination was requested, showed a 100% sensitivity and a 96% specificity of the dPT performed with Innovin, as compared to 81% and 93% respectively for the dPT using Simplastin.

Antiphospholipid Syndrome↗
PubMed2004

No deterioration after 13 years in a stability study of a rabbit brain, plain, thromboplastin, RBT 1010, in rubber-stoppered ampoules.

RBT 1010, a rabbit brain thromboplastin, plain, was prepared at the Thrombosis Reference Centre, Withington Hospital, Manchester, in 1989. The batch has been stored at -20 degrees C, in rubber-stoppered ampoules, for 13 years. The material was unchanged after this time. This was confirmed in a stability study, in which the reagent was used to test the prothrombin times of a panel of plasmas stored in liquid nitrogen, one from a normal volunteer and two from stable anticoagulated patients. RBT 1010 was also tested in calibrations, according to World Health Organization recommendations, against the reference thromboplastin preparations CRM 149S and RBT 90.

Animals↗
PubMed1976

The effect of intravenous injection of purified human tissue thromboplastin in rats.

As a background for the development and testing of phospholipase C in the therapy of post-traumatic and post-surgical intravascular coagulation, highly purified tissue thromboplastin was injected i.v. into rats. The levels of factor V, VII, VIII and blood platelets and the activity of the intrinsic coagulation pathway in general (the cephalin test) were followed. Histological examination of pulmonary, kidney and liver tissue was carried. The dose-response was highly dependent on the injection rate. A marked activation of factor VII and a fall in the activities of factors V and VIII as well as in thrombocyte counts were observed. Very few or no thrombi were seen beyond the pulmonary circulation. The main changes (fibrin-containing thrombi and platelet aggregates) were observed in the lungs during the first 15 min after injection. Atter 15 min virtually no thrombi or platelet aggregates could be detected. The effect of tissue thromboplastin was counteracted by large doses of antithrombin III.

Animals↗
PubMed1979

The varied sensitivity of partial thromboplastin and prothrombin time reagents in the demonstration of the lupus-like anticoagulant.

An acquired inhibitor of blood coagulation, similar to that described in patients with Systemic Lupus Erythematosus (SLE), was detected during routine coagulation screening in 10 patients who did not meet the criteria for a diagnosis of SLE. The lupus-like anticoagulant (LLAC) was diagnosed on the basis of prolonged activated partial thromboplastin time (APTT) and/or prothrombin time (PT) which failed to correct when patient plasma was added to normal plasma; an additional criterion was an abnormal tissue thromboplastin inhibition test. No patient had a specific inhibitor directed against factors VIII and IX. Demonstration of LLAC was highly dependent upon the type of reagents adopted in the APTT and PT: the abnormality was detected consistently by one reagent only. One-stage assays of factors VIII and IX were characteristic of the presence of an inhibitor, showing non-parellel dose-response curves or decreased activity at low dilutions which were partially corrected at higher dilutions. Although 7 patients were free of abnormal bleeding, unequivocal signs of haemorrhagic tendency after a surgery were present in the remaining 3 patients. The findings suggest that LLAC is a non-exceptional cause of prolonged coagulation screening tests, and that it may sometimes be associated with impaired haemostasis.

Adolescent↗
PubMed1980

Thromboplastin reference preparations.

The need for standardization of methods for the control of anticoagulant therapy was apparent 25 years ago. With the development of the ratio method for comparing the sensitivity of different thromboplastin preparations it became possible to equate the value obtained with one preparation in terms of the value which would be obtained with any other preparation, and the need for a reference to serve as a yardstick for comparison became obvious. The first trial reference preparation was developed in 1965 and three small international trials on the calibration of different thromboplastin preparations were conducted. The first international reference preparation was laid down in 1967 coded 67/40, and other preparations containing ox brain, human brain and rabbit brain and coded 68/434, 69/223 and 70/178 followed. Further collaborative studies were carried out in 1970 and 1973, and a large international trial undertaken in 1974, using 70/178 as the reference preparation. These preparations have remained stable over a period of 9 to 12 years and their usefulness for purposes of calibration and international trials has been proven. Three further reference preparations were laid down in 1979 and a further international collaborative study has been undertaken.

Animals↗
PubMed1970

Vasculas complications in nephrotic syndrome: relationship to steroid therapy and accelerated thromboplastin generation.

Arterial thrombosis and renal vein thrombosis occurred in two men and one woman, respectively, treated with steroids for the nephrotic syndrome. Raised serum cholesterol occurred in one patient only. Though bleeding, clotting, and prothrombin times, as well as the platelet counts, were normal, the rate of thromboplastin generation was increased in all three patients. Adding heparin to the plasma of one patient slowed the rate, and suggested that the raised rate could be due to removal or suppression of such normal circulating coagulation inhibitors. The thromboplastin generation test seems to be useful in diagnosing and managing such hypercoagulable states, and may help in further investigations of their causes.

Adult↗
PubMed2005

European Concerted Action on Anticoagulation. A multicentre calibration study of WHO international reference preparations for thromboplastin, rabbit (RBT/90) and human (rTF/95).

A 10 centre calibration was performed after six years to determine the international sensitivity index (ISI) of rTF/95 relative to RBT/90, and to assess any international normalised ratio (INR) bias compared with the original multicentre calibration. After exclusion of one outlying centre, the follow up calibration gave a mean ISI for rTF/95 of 0.99, which although a small difference, is significantly greater than the mean ISI of 0.94 obtained previously. The change in ISI for international reference preparation (IRP) rTF/95 relative to RBT/90 would lead to a slight bias in INR for human compared with rabbit thromboplastins. At a theoretical INR of 3.0, the INR bias is 6.0%, and this is below the accepted 10% level of clinical relevance. Ongoing stability monitoring of World Health Organisation thromboplastin IRP is advised.

Animals↗
PubMed1997

Monitoring oral anticoagulant treatment with the TAS near-patient test system: comparison with conventional thromboplastins.

BACKGROUND: A number of instruments have been developed for determination of prothrombin time (PT) and International Normalised Ratio (INR) at locations not limited to central laboratories. AIM: To evaluate one such portable instrument, the Thrombolytic Assessment System (TAS), which can be used in a near-patient setting. METHODS: Samples from 20 normal subjects and 48 patients treated with warfarin for venous thromboembolic disease were studied. The warfarin group was divided into: initiation phase (n = 10), combined warfarin and heparin (n = 10), stabilised therapy (n = 20), and over anticoagulated patients (n = 8). PTs and INRs were determined in each group using three conventional thromboplastins (Diagen Activated, Manchester Reagent, and Instrumentation Laboratory) and two TAS techniques (whole blood or plasma). An independent International Sensitivity Index (ISI) calibration of the TAS system was performed. RESULTS: Calculated ISIs for the TAS were 1.028 and 0.984 for plasma and whole blood analysis, respectively, compared with manufacturer's values of 0.98 and 0.97. INR results with TAS (whole blood) were 11% less than those obtained with Diagen Activated (p < 0.01) and 16% less than those obtained with Instrumentation Laboratory (p < 0.001) when manufacturers' mean normal PT and ISI were used for TAS INRs. TAS (whole blood) results were similar to TAS plasma or Manchester Reagent results. The use of a locally determined mean normal prothrombin time (MNPT) improved agreement between TAS and the other reagents, abolishing the significant difference between INRs determined with TAS (whole blood) and Diagen Activated techniques. CONCLUSION: The TAS system can be used with whole blood or plasma and produces similar INRs to those obtained with Diagen Activated or Manchester Reagent using manufacturer's ISI and a locally determined MNPT. Results were lower with TAS or Manchester Reagent compared with those obtained with Instrumentation Laboratory thromboplastin.

Anticoagulants↗
PubMedDate not supplied

Multiple intracranial hemorrhages at the time of a transiently prolonged activated partial thromboplastin time in an infant with congenital factor VII deficiency.

Factor VII (FVII) deficiency is a rare autosomal recessive hereditary disorder characterized by a normal partial thromboplastin time and a prolonged prothrombin time. For definitive diagnosis, the specific FVII level should be investigated. We report on a 7-month-old boy with congenital FVII deficiency suffering from convulsions and intracerebral hemorrhage. Hematologic tests revealed prolonged prothrombin time associated with a decreased FVII level of 1.7%. Computerized tomography of the brain revealed multifocal hemorrhagic lesions. To our knowledge, multifocal intracranial hemorrhages at the time of a transiently prolonged partial thromboplastin time of unknown origin in a child with congenital FVII deficiency of about 2% has not been reported so far.

Cerebral Hemorrhage↗
PubMed1979

Circulating tissue thromboplastin during hip surgery.

An immunoradiometric assay for tissue thromboplastin has been established. Blood levels in 6 patients undergoing total hip replacement have been determined. In 3 patients, high levels of circulating apoprotein III were found at various stages of the operation, showing a release of tissue thromboplastin chiefly during impaction of the prosthesis into the femoral bone. The other 3 patients had low or undetectable levels.

Adult↗
PubMed1975

[Solubilization of brain thromboplastin. Effect of different detergents].

The effect of 3 different detergents (Triton X-100, Lubrol WX and Nonidet) on brain thromboplastin was examined and compared with the solubilisation due to deoxycholate. The effect of deoxycholate is superior over that of the other examined detergents. Deoxycholate extracts thromboplastic activity from brain tissue to a large extent. Furthermore it has no interfering absorbance at 280 nm. The aminopeptidase of brain tissue may be separated from thromboplastin. It does not have any coagulation activity.

Aminopeptidases↗
PubMed1980

The antiheparin effect of alpha 1-acid glycoprotein, evaluated by the activated partial thromboplastin time and by a factor Xa assay for heparin.

The heparin-antagonizing effect of human alpha 1-acid glycoprotein (alpha 1-acid GP) was studied by activated partial thromboplastin time (APTT) and by a factor Xa assay for heparin using a chromogenic substrate for factor Xa. The antiheparin effect of alpha 1-acid GP in the APTT system was similar to the effect on heparin thrombin clotting time (HTCT), and the effect in the factor Xa assay system corresponded well with the effect in a heparin cofactor assay system using chromogenic substrate for thrombin instead of factor Xa. It is concluded that alpha 1-acid GP contributes to the reduced anticoagulant effect of heparin observed in various acute stages of disease, when assayed not only by HTCT but also by so-called 'global' coagulation tests, such as the activated partial thromboplastin time.

Antithrombins↗