Technical Objectives in the Control of Anticoagulant Therapy

Merskey, Clarence; Scholtz, Elizabeth

doi:10.1111/j.1365-2141.1955.tb05513.x

Cited by 3 publications

(1 citation statement)

References 25 publications

(5 reference statements)

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“…In addition to the original manual technique a large variety of automated instruments are now widely used (2,3). It was recognised as long ago as the early 1950s that the results of the prothrombin time showed poor agreement between centres (4)(5)(6)(7)(8). This situation has not changed and tissue thromboplastin reagents still differ greatly in response to the coumarin induced effect and this profoundly affects the oral anticoagulant dosage regimes and intensity of anticoagulation.…”

Section: Many Technical Changes and New Methods Specifically Designedmentioning

confidence: 99%

Questions and Answers on Prothrombin Time Standardisation in Oral Anticoagulant Control

Loeliger¹,

Poller

Samama

et al. 1985

Thromb Haemost

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SummaryOne of the reasons why oral anticoagulants fell into disrepute is the absence of internationally accepted standardised procedures for controlling the level of anticoagulatiori. This deplorable situation resulted in over- and under-coagulation and uncertainty in the therapeutic range. International conformity can now be obtained by using an International Normalised Ratio (INR) which is derived from the individual result obtained in a given plasma sample and the International Sensitivity Index (ISI) of the tissue thromboplastin reagent used. Any thromboplastin reagent can be calibrated against an international primary or secondary W.H.O. reference preparation, so as to obtain its International Sensitivity Index. The new system of reporting the level of anticoagulation was designed and can only safely be applied in patients taking oral anticoagulants.

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Section: Many Technical Changes and New Methods Specifically Designedmentioning

confidence: 99%

Questions and Answers on Prothrombin Time Standardisation in Oral Anticoagulant Control

Loeliger¹,

Poller

Samama

et al. 1985

Thromb Haemost

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Use of Different Tissue Thromboplastins in the Control of Anticoagulant Therapy

1957

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As anticoagulant therapy has become more widespread and a greater knowledge has been accumulated regarding the mode of action of coumarin derivatives, problems arising from the use of different thromboplastin preparations have been subjected to greater scrutiny. This paper presents an evaluation of the dependability and significance of different types of tissue thromboplastin in the determination of effects of coumarin derivatives. The main difference between thromboplastin extracts seems to be that brain preparations have a factor VII-like activity. As the exact evaluation of factor VII activity appears to be of primary importance in patients treated with coumarin derivatives, a thromboplastin preparation that does not contain factor VII activity is recommended.A THE indications for anticoagulant therapy become more extended, some problems in the management of anticoagulant therapy with coumarin derivatives and their laboratory control become increasingly important.Until recently very little was known about the mode of action of coumarin derivatives. It has been shown that the activity of factor VII and subsequently of prothrombin decreases during coumarin therapy. This diminution is usually directly related to the antithrombotic activity of coumarin derivatives. Douglas' has recently shown that the prothrombin level of the blood does not fall below 50 per cent of normal during adequate therapy with 3,3'-carboxymethylenebis (4 -hydroxycoumarin) ethyl ester (Tromexan). The prolongation of the prothrombin time by the 1-stage method is partly due to the deficiency of factor VII and the moderate depression of prothrombin is insufficient to decrease blood coagulability. Recent studies have also demonstrated that the activity of other clotting factors, such as plasma thromboplastin component (PTC, factor IX, Christmas factor)2' 3 and factor X4 5 decreases during coumarin therapy. The influence of coumarin derivatives on the latter 2 factors is not detected by the 1-stage prothrombin determination because potent tissue thromFrom the Vascular

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Analytical Review: Anticoagulant Therapy

Merskey

Drapkin

1965

Blood

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Technical Objectives in the Control of Anticoagulant Therapy

Cited by 3 publications

References 25 publications

Questions and Answers on Prothrombin Time Standardisation in Oral Anticoagulant Control

Questions and Answers on Prothrombin Time Standardisation in Oral Anticoagulant Control

Use of Different Tissue Thromboplastins in the Control of Anticoagulant Therapy

Analytical Review: Anticoagulant Therapy

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