A process for determining a resistance to activated
protein C of a test specimen of
human plasma following the steps of: (1) mixing together (a) the test specimen of
human plasma, (b) a reactant deficient in
factor V which supplies at least most of the coagulation factors other than
factor V, and (c) the
venom of Crotalus viridis helleri which specifically activates
factor X to Xa, and incubating the mixture of (a), (b) and (c) for at least one minute at a temperature of between 10 and 45° C.; (2) introducing into the incubated mixture(i) Ca2+ or (ii) Ca2++exogenic activated
protein C; and (3) determining the
coagulation time (i) in the absence of activated
protein C and (ii) in the presence of activated
protein C. Steps (1) to (3) are repeated, but replacing, in step (1), the test specimen with a normal
plasma as control and correlating resistance to activated
protein C by comparing the determinations made in steps for the test specimen and for the normal
plasma. The
initiation of coagulation is caused by activating
factor X to Xa using the
venom of Crotalus viridis helleri in the presence of (i) Ca2+ or (ii) Ca2++ exogenic activated
protein C.