An Assessment of an Amidolytic Assay for Factor VII in the Laboratory Control of Oral Anticoagulants

Abstract

A comparison has been made between the prothrombin time test using British Comparative Thromboplastin (BCT) and a chromogenic substrate assay for factor VII in the assessment of laboratory control of oral anticoagulants in short-term and long-term patients. Opportunity was also taken to compare the findings with parallel results obtained with the venous Thrombotest technique and a specific clotting assay for factor VII. There was good agreement between the amidolytic factor VII assay, using a method modified from Seligsohn et al (1978) with the Quick test using BCT and Thrombotest in 60 long-term patients. Tests in 53 patients within the first 3 weeks of starting oral anticoagulant administration gave less satisfactory agreement between the above amidolytic method and the conventional tests. In contrast, there was a good correlation between the two conventional tests in both groups and also between the clotting and amidolytic factor VII method. Although the results are an improvement on previous, less satisfactory correlations between the BCT prothrombin time method and amidolytic assays for factor II and X, the present study indicates the limitations of a specific clotting assay versus a broad spectrum extrinsic clotting test in oral anticoagulant control. While not warranting the routine use of the chromogenic assay for factor VII in place of the prothrombin time using BCT, the factor VII amidolytic assay offers a limited but dependable guide to dosage in long-term patients. The complexity of the technique in its present form militates against its adoption for routine anticoagulant control in hospital laboratories.

Laboratory Control of Anticoagulant Therapy

“…25 An amidolytic method for Factor VII gave better agreement, but again results were not as good in short-term treatment, although showing a reasonable correlation with the PT in long-term stabilized patients. 27 O'Donnell et al 28 found good agreement between a Factor II amidolytic method compared with BCT and Thrombotest, but this was also in stabilized patients. The reports showing good agreement with conventional clotting tests have been predominantly on long-term treated pa tients, but the main problems in control of dosage occur in the stabilization period.…”

Use of Chromogenic Peptide Substrates in the Determination of Clotting Factors II, VII, IX and X in Normal Plasma and in Plasma of Patients Treated with Oral Anticoagulants

“…Poller et al [12] observed a percentage agreement in diagnosis, assessed with Thrombotest and factor VII chromogenic ac tivity of 87.5% in patients receiving long term anticoagulant therapy.…”

“…The therapeutic range for Thrombotest was taken between 5 and 12.5%, the corresponding therapeutic range for factor X chromogenic activity was 180-300 U/l (18-30%) [ 11 ]. Poller et al [ 12] observed a good agreement between 1/Thrombotest and factor VII chromogenic activity in plasma; percentage agreement in diagnosis was 87.5%.…”

“…Until now in most experimental studies the chromogenic activity of only one of the vitamin K-dependent clotting factors has been compared to Thrombotest values [10][11][12][13] or to the clotting activity of the other vitamin K-dependent factors [10][11][12][13][14][15], In the present study the chromogenic activity of all four vitamin K-dependent factors was as sayed in healthy human subjects and in pa tients receiving oral anticoagulant drugs. The chromogenic activities of the vitamin Kdependent factors were correlated both among each other and with 1/Thrombotest.…”

Half-Life Time and Control Frequency of Vitamin K-Dependent Coagulation Factors

“…Clinical assays of factor VII and its activity state in plasma could be of great diagnostic importance [Hemker et al, 1976;Poller et al. 1981;Avvisati et al, 1980;Selig sohn et al, 1978b;Aiyappa, 1981a, b].…”