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

Abstract

Spectrophotometric methods were used to assay the clotting factors II, VII, IX and X in plasma of 33 subjectively healthy human donors and in plasma of 98 patients receiving long-term oral anticoagulant therapy. In 33 normal subjects the interindividual variations in the plasma activities of the clotting factors II, VII, IX and X are respectively 12.2, 21.4, 11.0 and 15.0%. After correction for the assay variations the remaining biological variations are respectively 11.7, 21.2, 9.7 and 14.8%. Plasma from 98 patients receiving long-term anticoagulant therapy was assayed with ‘Thrombotest’, a clotting test in whole blood introduced by Owren and in these plasmas the activity of each of the vitamin K-dependent factors was assayed with spectrophotometric methods. For the clotting factors IX and VII, novel spectrophotometric methods were applied and the plasma activities thus measured were compared to results obtained with factor IX and VII clotting assays. Chromogenic activities of the different factors were correlated among each other and with 1/Thrombotest values. When the therapeutic range for Thrombotest values is set between 5 and 12.5% the corresponding therapeutic ranges for the activity of the factors II, VII, IX and X are respectively 12.6–36.1, 27.0–52.3, 23.1–49.3 and 18.9–36.2% (expressed as a percentage of the activity in normal pool plasma). The chromogenic assays for the factors II, VII, IX and X provide the same information on the therapeutic state of the patients in respectively 86.7, 78.6, 81.6 and 89.8% of the cases. Finally we discuss the suitability of the different assays to monitor oral anticoagulant therapy.

Evaluation of an Automated Prothrombin Assay Using a Chromogenic Substrate

“…The preci sion of the automated assay was superior to that of the manual technique and the CV's obtained were comparable to those obtained with other automated systems [1,2,4,9], Highly significant correlations were ob tained when the assay was compared to the clotting tests which are routinely used for the control of oral anticoagulant therapy. Our estimate of the prothrombin therapeutic range is entirely consistent with that of another study (derived from Thrombotest range 5-12.5%) [10]. As the plasma samples tested in this investigation were from pa tients on long-term oral anticoagulant thera py, further studies will be required to estab lish the validity of the present assay for those patients in the early stages of anticoagulant therapy, when the levels of factor VII are more depressed than those of the other vitamin-K-dependent factors [11].…”

The Effects of Acetaminophen on Pharmacokinetics and Pharmacodynamics of Warfarin

“…For (R)-and (S)-warfarin, mean serum concentration-time profiles generated from each treatment were not found to be statistically different. Pooling the data from all treatments, the mean area under the curve was 50.03 ± 8.09 mg/L*hr for (R)-warfarin and 35.55 ± 9.54 mg/L*hr for (S)-warfarin, and this was statistically different (p < 0.05).…”

Spectrophotometric Method for the Assay of Human Blood Coagulation Factor VIII

“…Previously, we found a variation for factors VII, IX, X and prothrombin of 21.4, 11.0, 15.0, and 12.0%, respectively [18], suggesting that the factors VII and VIII present in plasma in the lowest concentration and the shortest half life tend to have the largest biological varia tion.…”

“…For prenatal diagnosis of hemophilia [14], the assay can easily be scaled down such that the test can be carried out with small plasma volumes obtained by fetoscopy [17,18],…”