Abstract: The invention concerns a process for the purification of factor VIII by affinity chromatography characterized in that a biological fluid containing factor VIII is contacted with immobilized cellular von Willebrand factor or a derivative thereof under such conditions that factor VIII is adsorbed to the immobilized von Willebrand factor or derivative thereof, impurities are separated and adsorbed factor VIII is eluted.

Abstract: In order to determine lupus anticoagulant (LA) antibodies in blood, plasma or tissue samples by means of the inhibitory effect of these antibodies on the neutralizing effect of protein C on the blood coagulation system, a defined amount of activated protein C is added to the sample, after incubation the remaining amount of a physiological substrate of protein C or protein S activity in the sample is determined according to known methods and the amount of LA antibodies present is calculated by comparison with a standard containing no LA antibodies. The method according to the present invention can be used to diagnose a predisposition to thrombotic events or disease-dependent risk of thrombosis as well as to monitor a therapy.