A method and kit are provided for monitoring
anticoagulant therapy based on measuring the simultaneous influence of factors II and X only, in a
test sample (i.e., test
plasma or
whole blood) of an anticoagulated patient, by creating a corrected sample that circumvents measuring also the influence of
fibrinogen,
factor V, and
factor VII on the clotting process in the corrected sample. One or more coagulation reagents that
activate factor VII or
factor X, but not
factor IX, are added to the corrected sample, and the
blood clotting ability of the corrected
plasma sample is subsequently determined by measuring
blood clotting time. Alternatively, a
reagent plasma with added
factor VII is mixed into the
reagent activator, such as
thromboplastin, that is subsequently added to a sample of test plasma or
whole blood to correct the
test sample and measure the simultaneous influence of only factors II and X.