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PubMed1986

Is duplicate testing for prothrombin time and activated partial thromboplastin time necessary?

To evaluate the necessity of duplicate testing for prothrombin times (PTs) and activated partial thromboplastin times (APTTs), the range of differences between duplicate sample results was analyzed on a widely used automated photo-optical coagulation instrument. Specimens with coagulation test times ranging from normal to threefold above the reference range were included. Of 1,610 PTs and 1,023 APTTs, approximately 95% of duplicates differed by 0.2 s or less and 2.0 s or less, respectively. Approximately 99% of PTs and APTTs differed by 0.4 s or less and 4.0 s or less, respectively; there were three PT and 16 APTT specimens whose duplicates differed by a greater time interval and also by more than 5% of the mean. Thus, PT and APTT testing on automated instrumentation is very precise, but occasional inaccurate single measurements could lead to errors in diagnosis or therapy.

Blood Coagulation Tests↗
PubMed1986

[Monitoring heparin therapy by thrombin time and activated partial thromboplastin time--a comparison].

In 106 plasma samples obtained from patients on heparin therapy, monitoring by 2 methods (activated partial thromboplastin time and thrombin clotting time--APTT and TT) was compared. All patients in whom APTT indicated markedly higher plasma heparin concentrations than the TT were critically ill (group B): their main diagnoses included severe infectious disease, severe liver disease and extensive myocardial infarction. Patients with lesser discrepancies between the results of APTT and TT did not suffer from such severe conditions (group A). Cardiac surgery without major postoperative problems, limited myocardial infarction and uncomplicated thromboembolism were the main diagnoses in this group. In group B, non-heparin related prolongation of APTT was thought to be the main factor responsible for the overestimation of plasma heparin concentrations by this test. We conclude that in patients with severe infectious disease, liver disease or extensive tissue necroses (i.e. myocardial infarction), APTT cannot be recommended for laboratory monitoring of heparin therapy.

Blood Coagulation Tests↗
PubMed1985

A comparison of heparin potency estimates obtained by activated partial thromboplastin time and british pharmacopoeial assays.

Heparin samples from five manufacturers were assayed by the revised British Pharmacopoeia (BP) heparin assay and the results compared with those obtained using the activated partial thromboplastin time (APTT) assay. The United States Pharmacopoeia (USP) reference heparin preparation and the 4th International Standard (IS) for heparin were also assayed by the two methods relative to the 3rd IS. The results obtained by the revised BP assay were in close agreement with those obtained by the APTT assay for all the heparins that were tested. The assays revealed that there is at least a 10% discrepancy between the International Unit for heparin and the USP unit.

Animals↗
PubMed1985

A clinical evaluation of automated chromogenic tests as substitutes for conventional prothrombin time and activated partial thromboplastin time tests.

Automated procedures involving a chromogenic substrate sensitive to thrombin-sarcosine-Pro-Arg p-nitroanilide were compared with conventional tests for prothrombin times and activated partial thromboplastin times (APTT) and with specific assays for factors V, VII, VIII, IX, X, XI, and XII. The reproducibility and sensitivity of the chromogenic tests were compared with those of the clotting tests. Further, we have confirmed that the chromogenic test for APTT is sensitive to factor VII deficiency, unlike the clotting test for APTT. This might be an advantage in monitoring orally anticoagulated patients. The ready availability of the automated equipment for performing the chromogenic tests suggests their potential for routine use. However, some discrepant results in certain patients with liver disease and in others with factor VIII inhibitors warrant caution.

Autoanalysis↗
PubMed1985

Effect of sodium heparin and antithrombin III concentration on activated partial thromboplastin time in the dog.

Regulation of blood coagulation was studied in 12 dogs, using subcutaneous administration of sodium heparin. Dosage of heparin needed to achieve the desired 1.5- to 2.5-fold increase in the activated partial thromboplastin time (APTT) was 250 to 500 IU/kg of body weight. Increased APTT lasted less than 6 hours. Repeated heparin administration, using the lowest dosage (250 IU/kg) every 6 hours, induced an unacceptable prolongation of clotting times during the first 2 days of treatment. Prolonged administration at a dosage of 200 IU/kg every 6 hours adequately maintained the desired hypocoagulative state initially; after 2 days, however, the prolonged APTT steadily decreased. The decreasing effect was proportionate to a decrease in plasma antithrombin III (AT III). To sustain a correctly balanced hypocoagulative state from prolonged subcutaneous administration of heparin, APTT values should be determined regularly to monitor therapy. In addition, transfusion of AT III-rich donor plasma may be necessary when low plasma AT III reduces the effects of heparin.

Animals↗
PubMedDate not supplied

Clotting, activated partial thromboplastin and coagulation times in monitoring heparin therapy.

The automated-activated coagulation time, manual-activated coagulation time and the activated partial thromboplastin time were compared to the whole blood clotting time in the measurement of hypocoagulation of heparinized blood. The normal ranges and degree of reproducibility were determined for each clotting assay. Each method was examined for its sensitivity to various concentrations of heparin. In addition, blood samples from patients treated with heparin were assayed by all four methods and their results were compared. The results indicated that the manual-activated clotting time correlated best with the whole blood clotting time, was sensitive to low concentrations of heparin, formed a discernible clot within a convenient time period in blood containing high concentrations of heparin, was reproducible and was easily performed.

Blood Coagulation Disorders↗
PubMed1979

Role of tumor thromboplastin in the mode of distribution of metastatic foci in the lung.

Crude tumor cell extract from rat ascites hepatoma AH130 revealed a high thromboplastic activity. Intravenous injection of the extract caused widespread thrombus formation in the capillaries, arterioles, and arteries of the lung. Intravenous inoculation of AH130 after an injection of the tumor cell extract produced metastatic foci in the larger arteries, compared with the case injected with only AH130 which developed metastatic foci mainly in and around the alveolar septa. These results suggest the role of tumor thromboplastin material in the mode of distribution of metastatic foci in the lung.

Animals↗
PubMed1975

Species specificity of thromboplastin. A phylogenetic study.

Having studied the influence of thromboplastin preparations derived from cold and warm-blooded species on the plasma of 12 vertebrates (carp, frog, turtle, hen, rabbit, rat, mouse, guinea-pig, ground squirrel, dog, sheep and man) we have established that among the species far from each other phylogenetically, the phenomenon of species specificity could be demonstrated in general. It was found that the extrinsic coagulation system measured by Quick times can well be activated in every examined species. Simultaneously, in plasmas of turtle and hen the intrinsic clotting system proved to be deficient.

Animals↗
PubMed1971

Monitoring heparin therapy with the activated partial thromboplastin time.

Difficulties associated with the whole blood clotting time (W.B.C.T.) as a method of monitoring heparin therapy have led to the investigation of the activated partial thromboplastin time (A.P.T.T.) as an alternative. The conclusion is reached that the latter procedure possesses several advantages. Using the method described and a citrate-preserved blood sample collected just prior to the administration of the next serial dose of heparin, the suggested therapeutic duration of the A.P.T.T. is 70 seconds or twice the mean control value. A practical range for this method is 60 to 70 seconds.

Administration, Oral↗
PubMed1977

Spurious prolongation of the activated partial thromboplastin time.

The clinical and laboratory data of 8 patients (4 males and 4 females) with circulating anticoagulant were presented. Based on prolonged APTT, failure to correct the APTT with 50% normal plasma and abnormal tissue thromboplastin inhibition test, the inhibitor was identified as "middle stage"--or the "lupus anticoagulant". Thrombokinetics showed the maximal rate of change in optical density (VmaxdeltaOD) of plasma, resulting from clot formation to be significantly less in the plasma of patients with the inhibitor than in normal plasma. This was not completely corrected by mixing the patients' plasma with 50% normal plasma.

Adult↗
PubMed1983

Effect of cyclic AMP and cyclic GMP on thromboplastin (factor III) synthesis in human monocytes in vitro.

Human monocytes in vitro respond to various agents (immune complexes, lectins, endotoxin, the divalent ionophore A 23187, 12-O-tetradecanoyl-phorbol 13-acetate [TPA], purified protein derivative [PPD] of Bacille Calmette-Guerin) with an increased synthesis of the protein component of thromboplastin. The effect of cyclic AMP and cyclic GMP on this response has been studied. Dibutyryl-cyclic AMP, prostaglandin E1 and the phosphodiesterase inhibitors 3-butyl-1-methyl-xanthine (MIX) and rac-4-(3-butoxy-4-methoxybenzyl)-2-imidazolidinone (Ro 20-1724), separately and in combination have a pronounced inhibitory effect on the response to immune complexes and PPD, and a moderate effect on the response to endotoxin and lectins. The effect on TPA response and on the response to A 23187 was slight. Dibutyryl-cyclic GMP (1 mM) gave a slight inhibition of the TPA and IC response, but had essentially no effect on the response to other inducers. The intracellular cAMP level increased when monocytes were incubated with IC, TPA or A 23187 followed by a decrease to basal levels within 1-2 hr, whereas lectin (PHA) and PPD did not induce such changes. The cAMP response to endotoxin varied. Stimulation with IC induced an increase in monocyte cGMP levels, whereas the other stimulants did not cause such changes.

Cells, Cultured↗
PubMed1984

Interaction of thromboplastin apoprotein of different tissues with concanavalin A--evidence for heterogeneous glycosylation of the human apoprotein.

Thromboplastin apoproteins of different tissues were solubilized with Triton X-100. Induction of plasma coagulation by these extracts was dependent on the presence of factor VII. Binding of the apoprotein-Triton complex to Concanavalin A-Sepharose 4B was studied. The apoprotein activity extracted from rabbit brain and bovine brain was almost completely bound to Concanavalin A-Sepharose. Under the same conditions, only partial binding was observed with human lung, human brain and human placenta apoproteins. These results suggest that human apoprotein is heterogeneous with respect to its carbohydrate moiety.

Animals↗
PubMed1984

[Circulation of tissue thromboplastin in the blood].

Tissue thromboplastin injected i.v. in the form of microsomal fraction of the aorta intima was rapidly eliminated from the blood flow but did not enter into the lymph in any considerable amount. The disintegration products of the microsomal fraction of the aorta intima are released into the blood flow mostly within 5 days as revealed by the 5'-nucleotidase activity.

Animals↗
PubMed1978

Comparison of prothrombin time and activated partial thromboplastin time on Dade Auto-FI and Bio-Quest Fibrometer.

Plasma assay results for prothrombin time and activated partial thromboplastin time obtained on the fully automated Dade Auto-FI were compared with those obtained on the more traditional semi-automated Bio-Quest Fibrometer. The precision data showed in a majority of cases the superior reproducibility of the Auto-FI over the fibrometer. However, we found that results of APTT utilizing both methodologies were not at present interchangeable.

Blood Coagulation Tests↗
PubMed1983

Urothromboplastin evidence for similarity between urothromboplastin and human brain thromboplastin.

Urothromboplastin (UP) is a lipoprotein similar to Human Brain Thromboplastin (HBrTPL), the specific activity being bound to the presence of the whole complex. UP is found in normal human urine to be macroaggregates, therefore the substance is eluted from the Sepharose 2 B column immediately after the void volume and is found in the bottom of the tube after ultracentrifugation. In polyacrylamidgelelectrophoresis UP does not enter the gel and the UP activity can be eluted from the top of the gel. Natrium-desoxycholate reduces the activity of UP greatly, however after removal of this substance the original activity could be regained. There are similarities between UP and HBrTPL: In the same way as HBrTPL UP acts in the extrinsic pathway of the coagulation system, some evidence for binding of factor VII to UP in the presence of calcium could be found. Anti-apoprotein III antiserum (anti-HBrTPL antiserum) neutralizes UP, depending on the concentration of the antiserum. The same antiserum precipitates with UP using the immunodiffusion method.

Apoproteins↗
PubMed1984

The activated partial thromboplastin time of diluted plasma: variability due to the method of fibrin detection.

The purpose of this study was to determine the effects of the dilution of plasma (1/3 in saline) on the kinetics of fibrin generation in the activated partial thromboplastin time (APTT) assay. The diluted APTT is considered to increase the sensitivity of the APTT test however, studies in our laboratory using an electro-optical fibrin detection system failed to show significant differences in APTT values obtained with diluted and undiluted canine plasma. Seventeen plasmas, including plasmas moderately and markedly deficient in intrinsic factor activity were assayed in the undiluted and diluted APTT assay using two methods for fibrin endpoint detection; a visual "tilt-tube" technique and an electro-optical detection system. In the former technique the endpoint was the formation of a visible fibrin web or clot; in the latter procedure the end point was the first detection of a change in optical density of the plasma. Optical density changes during fibrin formation were also recorded ( thrombokinetograms ). The results indicated that the electro-optical fibrin detection system failed to identify a prolongation of the APTT as a result of 1/3 plasma dilution; a prolongation that was consistently observed with the visual fibrin detection technique. Plasma dilution however, did significantly reduce the rate of fibrin production as indicated by the thrombokinetogram profile. It was concluded that the dilution of plasma with saline, as has been used to increase the sensitivity of the APTT assay procedure, has little effect on the time of onset of fibrin formation in a given plasma. The major effect appears to be on the way in which fibrin forms in that the polymerization/crosslinkage events associated with macroscopic fibrin production are delayed.

Animals↗
PubMed1980

Activated partial thromboplastin time. A multicenter evaluation of 11 reagents in the screening of mild haemophilia A.

An internationally standardized preparation and 10 commercial kits widely used to perform the activated partial thromboplastin time (APTT) were compared in 4 laboratories for the purpose of assessing their ability to detect mild deficiencies of factor VIII activity. The participating laboratories were asked to carry out with each APTT reagent quadruplicate readings of 3 coded lyophilized plasmas containing varying levels of factor VIII (109, 26 and 17 U/dl respectively). An analysis of variance of clotting times showed significant differences between reagents and laboratories. All the reagents detected the abnormality of the plasma containing 17 U/dl, whereas a number of failures were found when the plasma with 26 U/dl was tested. When analysis of variance was carried out on ratios of factor-VIII deficient to normal plasma clotting times, the results showed less difference between laboratories and reagents. Clotting times of plasma with normal factor VIII level (109 U/dl) usually fell within the normal range indicated by manufacturers of the commercial reagents.

Blood Coagulation Tests↗
PubMed1978

[Physiologic properties of heparin--thromboplastin complex].

The complexes of heparin with components of tissue thromboplastine occurring in vivo and in vitro, reveal an anticoagulating and antipolymerizational effects as well as a nonfermentative fibrinolytic activity. The latter becomes obvious in presence of proteinase inhibitors. On i. v. administration, the complex increases the fibrinolytic and anticoagulating properties of the blood. Its nonfermentative fibrinolytic activity in the bloodstream lasts for 60--90 min.

Animals↗