An Antithrombin III Assay Based on Factor Xa Inhibition Provides a More Reliable Test to Identify Congenital Antithrombin III Deficiency Than an Assay Based on Thrombin Inhibition

1993 ◽  
Vol 69 (03) ◽  
pp. 231-235 ◽  
Author(s):  
Christine Demers ◽  
Penny Henderson ◽  
Morris A Blajchman ◽  
Michael J Wells ◽  
Lesley Mitchell ◽  
...  
Keyword(s):  
Dna Analysis ◽  
Antithrombin Iii ◽  
Polyacrylamide Gel Electrophoresis ◽  
Factor Xa ◽  
Chromogenic Substrate ◽  
Cross Sectional ◽  
Thrombin Inhibition ◽  
Factor Xa Inhibition ◽  
At Iii ◽  
The Difference

SummaryObjectives: To determine whether functional antithrombin III (AT-III) levels measured by a factor Xa inhibition (AT-III-Xa) assay identifies AT-III deficient individuals more reliably than functional AT-III levels measured by a thrombin inhibition (AT-III-IIa) assay.Study design: Cross-sectional study.Patient population: Sixty-seven members of a large family with type 2 AT-III deficiency.Intervention: DNA analysis was used as the reference diagnostic standard for AT-III status and subjects were classified as AT-III deficient or non deficient according to these results. Functional AT-III levels were measured in all subjects using: 1) a chromogenic substrate for thrombin and added human thrombin (AT-III-IIa), and 2) a chromogenic substrate for factor Xa and added bovine factor Xa (AT-III-Xa). Functional heparin cofactor II (HC-II) levels were measured using a commercially available kit. The proportions of 125I-α-thrombin complexed to AT-III and HC-II were measured by polyacrylamide gel electrophoresis and autoradiography.Results: Thirty-one (46%) individuals were classified as AT-III deficient and 36 (54%) as AT-III non deficient. AT-III-Xa assay measured a significantly lower mean AT-III value and a narrower range for individuals classified as AT-III deficient than the AT-III-IIa assay. Using the AT-III-IIa assay, six subjects had borderline AT-III levels compared to none with the AT-III-Xa assay. Thrombin inhibition by HC-II likely accounts for the AT-III-IIa assay giving higher values than the AT-III-Xa assay since 1) there was a significant correlation between the difference in AT-III-IIa and AT-III-Xa levels and HC-II levels, 2) the mean level of HC-II was significantly higher for individuals who had a positive difference between AT-III-IIa and AT-III-Xa levels compared to those who had a negative difference and 3) there was a significant correlation between the difference in AT-III-IIa and AT-III-Xa levels and the percentage of 125I-α-thrombin complexed to HC-II.Conclusion: The AT-III-Xa assay is a better discriminant between AT-III deficient and AT-III non deficient individuals than the AT-III-IIa assay.

Reactivity of a Hereditary Abnormal Antithrombin III Fraction in the Inhibition of Thrombin and Factor Xa

1980 ◽  
Vol 44 (02) ◽  
pp. 092-095 ◽  
Author(s):  
T H Tran ◽  
C Bondeli ◽  
G A Marbet ◽  
F Duckert
Keyword(s):  
Antithrombin Iii ◽  
Factor Xa ◽  
Heparin Binding ◽  
Thrombin Inhibition ◽  
Superficial Thrombophlebitis ◽  
Heparin Concentration ◽  
Heparin Binding Site ◽  
At Iii ◽  
The Difference ◽  
Inhibition Of Thrombin

SummaryTwo different AT-III fractions were purified from the plasma of a patient with recurrent superficial thrombophlebitis. The abnormal AT-III fraction (A-AT) was compared to the normal AT-III fraction (N-AT) in the inhibition of thrombin and factor Xa. Without heparin, both inactivate proteases in a similar manner and at the same rate. However, at low heparin concentration the thrombin inhibition proceeds more slowly with A-AT than with N-AT. At high heparin concentration the difference between A-AT and N-AT becomes very small. The inhibition of factor Xa follows a similar pattern. It is suggested that the heparin binding site of A-AT differs from that of N-AT resulting in a decreased heparin cofactor activity.

Increased concentrations of heparin cofactor II in diabetic patients, and possible effects on thrombin inhibition assay of antithrombin III.

1989 ◽  
Vol 35 (1) ◽  
pp. 52-55 ◽  
Author(s):  
J Gram ◽  
J Jespersen
Keyword(s):  
Antithrombin Iii ◽  
Factor Xa ◽  
Diabetic Patients ◽  
Type I ◽  
Inhibition Assay ◽  
Heparin Cofactor Ii ◽  
Thrombin Inhibition ◽  
Factor Xa Inhibition ◽  
At Iii ◽  
High Concentrations

Abstract We compared concentrations of antithrombin III (AT-III) in plasma, as determined by an immunological method and by a functional thrombin inhibition method, in the presence of heparin in 160 blood samples from Type I diabetics. Although the correlation was highly significant (P less than 0.001) between the results obtained by the two methods, our data demonstrated that results by the thrombin inhibition assay, 121 (SD 15)%, expressed as percentages of the results for a normal plasma pool, were significantly (P less than 0.001) higher than by the immunoreactive method, 104 (SD 15)%, indicating an overestimation of functionally active AT-III. Concentrations of functionally active AT-III determined by a factor Xa inhibition assay, 105 (SD 13)%, were in the same range as immunoreactive AT-III. Addition of IgG antiserum to normal pooled plasma quenched only about 90% of the AT-III activity determined by the thrombin inhibition assay, but all of the AT-III activity determined by a factor Xa inhibition assay. These results demonstrate that the factor Xa inhibition assay is more specific for the determination of AT-III than the thrombin inhibition assay. We suggest that the high concentrations of heparin cofactor II, 117 (SD 17)%, might have caused an overestimation of AT III in this group of patients with diabetes Type I, and should not be overlooked in other clinical situations.

GAGs-Potentiated Inhibition of Thrombin, Factor Xa and Plasmin in Plasma and in a Purified System Containing Antithrombin III – Correlation with Total Charge Density

1981 ◽  
Vol 46 (04) ◽  
pp. 749-751 ◽  
Author(s):  
E Cofrancesco ◽  
A Vigo ◽  
E M Pogliani
Keyword(s):  
Charge Density ◽  
Chemical Structure ◽  
Antithrombin Iii ◽  
Factor Xa ◽  
Total Charge ◽  
Pure System ◽  
At Iii ◽  
Total Charge Density ◽  
The Difference ◽  
Inhibition Of Thrombin

SummaryThe ability of heparin and related glycosaminoglycans (GAGs) to accelerate the inhibition of thrombin, factor Xa and plasmin in plasma and in a purified system containing antithrombin III (At III) was studied using chromogenic peptide substrate assaysThere was a good correlation between the charge density of the mucopolysaccharides and the activities investigated. While the difference between potentiation of the antithrombin activity by GAGs in plasma and in the purified system was slight, the inhibition of factor Xa in plasma was more pronounced than in the presence of purified At III, indicating the mechanisms for GAGs-potentiated inhibition of thrombin and factor Xa are not identical.For the antiplasmin activity, there was a good correlation between the chemical structure and biological activity only in the pure system, confirming that the antithrombin-GAG complex plays a very limited role in the inactivation of plasmin in plasma.

Antithrombin III Avranches, a New Variant with Defective Serine-Protease Inhibition - Comparison with Antithrombin III Charleville

1988 ◽  
Vol 60 (01) ◽  
pp. 094-096 ◽  
Author(s):  
M Aiach ◽  
M Roncato ◽  
G Chadeuf ◽  
P Dezellus ◽  
L Capron ◽  
...  
Keyword(s):  
Antithrombin Iii ◽  
Factor Xa ◽  
Kinetic Studies ◽  
Exchange Chromatography ◽  
Protease Inhibition ◽  
Sds Page ◽  
Recurrent Venous Thromboembolism ◽  
Factor Xa Inhibition ◽  
New Variant ◽  
At Iii

SummaryA decreased plasma antithrombin activity in presence or in absence of heparin was discovered in a 47-year-old patient presenting with recurrent venous thromboembolism. The immunoreactive material (AT ΠΙ-IR) was normal. The same biological abnormalities were found in two relatives of the patient, leading to the diagnosis of hereditary qualitative AT III deficiency.The propositus’ AT III was coeluted with normal AT III from an heparin-sepharose column. An additional step of ion-exchange chromatography on a Mono Q column using a FPLC system (Pharmacia, St-Quentin en Yvelines, France) allowed the purification of a protein which was homogenous in SDS-10% polyacrylamide electrophoresis gel (PAGE). AT III purified from propositus’ plasma, normal plasma and the plasma of the patient known to have an AT III variant with defective protease binding (AT III Charleville) were compared. The specific activities measured as heparin cofactor anti thrombin or factor Xa inhibition in absence of heparin were decreased to half the normal value.Kinetic studies confirmed a decreased rate of thrombin inhibi-tion for both abnormal AT III preparations. SDS-PAGE experi-ments performed in purified system and immunoblots obtained from plasma showed that the two variants have different behaviour: in the case of AT III Charleville thrombin induced an apparent 5 Δ increase in molecular mass, probably due to a conformational change. AT III Avranches did not form stoechiometric complexes with thrombin, but was unmodified by the protease.

Development and characterization of an automated assay of effective heparin activity in plasma.

1987 ◽  
Vol 33 (9) ◽  
pp. 1630-1634 ◽  
Author(s):  
J F Pierson-Perry ◽  
D M Obzansky ◽  
J P Mizzer
Keyword(s):  
Antithrombin Iii ◽  
Factor Xa ◽  
Sole Source ◽  
Chromogenic Substrate ◽  
Blood Components ◽  
Automated Assay ◽  
At Iii ◽  
Assay Result ◽  
Heparin Activity

Abstract We describe a fully automated assay for determining effective heparin activity in plasma, based on heparin-catalyzed inhibition of Factor Xa (EC 3.4.21.6) by antithrombin III (AT III). Residual Factor Xa is determined kinetically by the Du Pont aca discrete clinical analyzer with a chromogenic substrate and is inversely related to heparin activity. Because the test plasma is the sole source of AT III, the assay result is dependent on AT III activity and reflects effective rather than total heparin activity. The assay range is 20-1200 USP units/L, and the assay shows equivalent sensitivity to standard and low-molecular-mass heparins. Within-run reproducibility (CV) is 1.6% at 390 units/L. There was no interference from common blood components or drugs. Results agreed well with those by the Coatest heparin kit (Kabi) adapted to the Cobas-Bio analyzer (r = 0.85, n = 122).

Measurement of Markers of Activated Coagulation in Antithrombin III Deficient Subjects

1992 ◽  
Vol 67 (05) ◽  
pp. 542-544 ◽  
Author(s):  
Christine Demers ◽  
Jeffrey S Ginsberg ◽  
Penny Henderson ◽  
Fred A Ofosu ◽  
Jeffrey I Weitz ◽  
...  
Keyword(s):  
Antithrombin Iii ◽  
Factor Xa ◽  
Large Family ◽  
Cross Sectional Study ◽  
Cross Sectional ◽  
Mean Values ◽  
Factor Xa Inhibition ◽  
Antithrombin Iii Deficiency ◽  
The Mean

SummaryFunctional antithrombin III levels were measured by factor Xa inhibition in 63 members of a large family with type 2 antithrombin III deficiency and individuals were classified as antithrombin III deficient or non-deficient according to the results. FI+2 and TAT complexes were measured using an ELISA and FPA levels were measured by radioimmunoassay.Thirty subjects (48%) were classified as antithrombin III deficient and 33 (52%) as antithrombin III non-deficient. The mean level of FI+2 was significantly higher in the deficient adults (0.87 ± 0.26) compared to both the non-deficient adults (0.70 ± 0.21) (p = 0.03) and the deficient adults receiving warfarin (0.16 ± 0.01) (p <0.001). The differences in the mean values of TAT complexes and FPA between deficient and non-deficient individuals were not statistically significant.These findings suggest that untreated antithrombin III deficient subjects generate more thrombin than their non-deficient family members and that warfarin inhibits this thrombin formation. In this cross-sectional study, it is not possible to correlate the levels of the surrogate makers with future clinical outcome.

HEPARIN COFACTOR II: A SIMPLE ASSAY METHOD

1987 ◽  
Author(s):  
H Vinazzer ◽  
U Pangraz
Keyword(s):  
Antithrombin Iii ◽  
Factor Xa ◽  
Tris Buffer ◽  
Assay Method ◽  
Healthy Individuals ◽  
Heparin Cofactor Ii ◽  
Complete Inactivation ◽  
Thrombin Activity ◽  
At Iii ◽  
The Difference

A photometric assay method for heparin cofactor II (HC II) is described. In a first step antithrombin III (AT III) in plasma is blocked by an anti human AT III immunoglobuline from goats. After dilution of this plasma with Tris buffer pH 8.4 containing 3 IU/ml heparin and addition of thrombin the remaining thrombin activity is measured by use of the chromogenic substrate S-2238 Kabi. The following preliminary experiments were carried out: Variation of the amount of anti-AT III added to plasma resulted in complete inactivation of 1.25 units AT III by 1.0 ml of the inhibitor. Incubation of 1 ml anti AT III with 1 ml purified AT III ( 1 U/ml} or with 1 ml normal plasma completely abolished AT III activity within 60 sec. Incubation of the reaction mixture with thrombin resulted in maximum inactivation after 180 sec. This is in contrast to AT III activated by heparin which immediately inactivates thrombin. Anti-Xa activity after depletion of AT III was assayed in a similar way by addition of factor Xa to the reaction mixture and measuring the remaining Xa activity by the substrate S-2222. In these tests no anti Xa-activity was found after AT III depletion. From these experiments there was assumed that the anti thrombin activity measured under the following conditions was due to the action of HC II:Plasma ( 50 μl) was mixed with anti AT III (50 μl) and was incubated for 60 sec. Tris buffer with heparin pH 8.4 (900 μl) was added. From this mixture 200 μl was pipetted into a cuvette at 37°C followed by 200 μl thrombin ( 2 IU/ml). After an incubation time of 180 sec 200 μl S-2238 ( 2 mmol/1) was added and the difference in OD/min was determined at 405 nm. A calibration curve was made by series of dilutions of normal AT III depleted plasma from 20 healthy individuals. The following preliminary results ofrHC II activity as a percentage were obtained:

Coagulation Inhibitors Studied with Chromogenic Substrate

1975 ◽  
Author(s):  
U. Abildgaard ◽  
M. Lie ◽  
A. Teien ◽  
O. R. Ødegård
Keyword(s):  
Sensitivity And Specificity ◽  
Antithrombin Iii ◽  
Factor Xa ◽  
Combined Effect ◽  
Assay System ◽  
Chromogenic Substrate ◽  
Reversible Inhibition ◽  
Heparin Treatment ◽  
At Iii ◽  
Coagulation Inhibitors

The rapid amidolysis of the chromogenic substrate Bz-Phe-Val-Arg-pNA by thrombin (Svendsen & al. Thromb. Res. 1, 267, 1972) provides a useful tool for the study of coagulation inhibitors. With purified reagents, reversible inhibition of the reaction can be demonstrated with 0.01 U/ml of heparin. The inactivation of thrombin by antithrombin III (At-III) is accelerated by 0.001 U/ml of heparin, making it possible to assay small amounts of heparin. The amidolytic assay system has also been used to study the competition between thrombin and factor Xa for At-III.The sensitivity and specificity of rapid amidolytic methods for assay of the following plasma activités will be reported:1) At-III activity (contaminating heparin neutralized).2) Exogenous heparin (during heparin treatment).3) Combined effect of At-III and exogenous heparin.4) At-III in the presence of optimal concentrations of heparin.

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