Experience Of Control Of The Initiation Of Coumarol Therapy With An Amidolytic Assay Of Factor X

Most authors agree that probably any of the vitamin K dependant factors can be used for control of coumarol therapy at steady state of treatment. However, during initiation of coumarol therapy poor correlations have been found between one stage prothrombin assays and specific factor analyses (II and X) and thus the usefulness of the specific assays in the initial phase of treatment has been questioned.

Purpose of study To investigate if a specific factor X analyses could be used for control of the initiation of coumarol (warfarin) therapy.

Methods Thrombotest (Nyegaard AS, Oslo). Amidolytic factor X assay according to Bergström and Egberg.

Patients admitted to the hospital because of venous thrombosis and/or pulmonary embolism. At present 13 patients (9 men, 4 women), age 36-81 years.

Design of study Heparin therapy was started as soon as the diagnosis was assigned. Warfarin treatment was commenced on the following day. Thrombotest and factor X was determined before and daily for 6 days after coumarol therapy was started. Only the results from the factor X analyses were given to the doctor in charge of the patients for monitoring of the coumarol therapy.

Results Thrombotest and factor X values generally fell in parallell except when high concentrations of heparin in the blood samples inhibited the Thrombotest method. The correlation between Thrombotest and factor X in 10 patients was good (r 0.81-0.99, mean 0.94).(Three patients were excluded for different reasons). The doctor in the ward found it as easy to monitor coumarol treatment with the factor X assay as with the Thrombotest. No bleeding or thromboembolic complications occurred.

Conclusion The amidolytic factor X assay could be used for monitoring coumarol treatment in the initial phase of treatment. The absence of sensitivity to heparin was regarded an advantage to the Thrombotest method.