Use of different tissue thromboplastins in the control of anticoagulant-therapy.

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.