Factor VIII in blood plasma of haemophilic sheep: analysis of clotting time-plasma dilution curves.

The sheep haemophilia A, recently described in a flock of White Alpine sheep, is probably caused by the production of a less potent mutant of factor VIII (F-VIII). Other potential mechanisms, such as drastic reduction (or lack) of F-VIII production, or occurrence of an F-VIII inhibitor, are less likely. This conclusion was based on the analysis of plasma dilution-clotting effect relationships in normal female (anestrous, non-pregnant) sheep, female carriers of haemophilia A, and afflicted male sheep. A response model underlying the analysis was suggested, its validity tested, and a mathematical analysis suitable for routine evaluation procedure recommended.