The relationship between Normotest and Thrombotest in patients on oral anticoagulant therapy

Normotest (sample volume: 25 micronl) and Thrombotest were performed in parallel on 150 consecutive capillary blood samples from patients on long term oral anticoagulant therapy. The ratio of Normotest to Thrombotest decreased from 2.50 at a Thrombotest level of 5-5.5% to 1.95 at a Thrombotest level of 13-13.5%, indicating that the effects of PIVKA were more pronounced at lower levels of coagulation activity. The influence of varying sensitivity of the thromboplastin reagents to PIVKA is discussed. The therapeutic range of Thrombotest (5-10%) corresponded to a Normotest level of 12-20%.