Method for specifically detecting a coagulation factor V which has an increased stability toward activated protein C in the activated state

A method for the determination of the stability of a coagulation factor v (F V) in its activated form (F Va) toward proteolytic degradation in a sample of a biological fluid, which method includes the following steps:

• a) mixing the sample with a reagent A, which has a lower content of functional F V than normal, human plasma;
• b) adding a reagent B which activates F V in the sample;
• c) adding a reagent C for proteolytically degrading the F Va in the sample;
• d) adding reagents necessary for determining F Va activity;
• and
• e) determining the activation of prothrombin to form thrombin by either detection of clot formation or by measuring conversion of a chromogenic thrombin substrate;
• wherein
• i) the volume of the sample of a biological fluid is 20% or less of the total volume of sample and all reagents added to the sample (test mixture);
• and
• ii) the steps a) through d) are performed without being interrupted by periods for incubating the resulting mixtures.