Computerized Analysis of the in vitro Activation of the Plasmatic Clotting System

Abstract

We analyzed the kinetics of the clotting system by a chromogenic substrate method in plasma with isolated factor deficiency. The sigmoidal extinction curve obtained was mathematically described by an equation with four constants K(i) relating to the activity of clotting factors and to the concentration of fibrinogen. The analysis of constants obtained from dilution series of factor-deficient plasma revealed a distribution pattern differing from one factor to another both for the extrinsic and the intrinsic system. The observations indicated that isolated factor deficiency may be identified through the analysis of 2 of the 4 constants, K(1) being the time value of the point of inflection of the extinction curve and K(2) a measure for the slope of the curve at the point of inflection. The observation was confirmed by a reclassification through nearest-neighbor discriminant analysis of K(1) and K(2) which revealed a correct classification in the pathological range for all factor deficiencies investigated with the exception of factors VIII and IX, the distribution patterns of which were superposed within the limits of distribution.

Simulation of the Extrinsic Pathway of the Plasmatic Clotting System

“…transformation of fibrinogen to fibrin [7], According to these experiments, K(l) in creases whereas K(2) decreases with increas ing fibrinogen concentrations. However, the distribution of the K(2)/K(l) patterns for isolated factor deficiency remains qualita tively unchanged.…”

“…Therefore, the equations describing the for mation of the complexes need not to be included in the model. Interactions between the extrinsic and intrinsic clotting system are ignored, since the results from the experiments indicated that the extrinsic sys tem is not significantly affected by factor VIII and factor IX deficiency [7], The feedback reaction on factor V via factor Ila and the formation of the prothrombinase complex can be introduced by equations, which describe the termolecular mechanism of action:…”

“…K ( 1): time value at the point of inflection of the curve; K (2): measure for the slope of the curve at the point of inflection (the slope at the point of inflection is defined: 0.5-K(2)-K(4)); K (4): amplitude of the ex tinction curve (the amplitude has been named K. (4) for reasons of comparability with Baumann et al [7].) E: extinction, and t: time.…”

“…Minor deviations are apparent at the beginning and at the end of the change of extinction between the fit in the curve for 1 % fac tor X deficiency; these, however, are not relevant for the calculation of the values for K(l) and K(2). The plots of the constants were compared with the plots from experimental data taken from Baumann et al [7] (fig-2).…”

“…Such experiments revealed discrete patterns separating one isolated clotting factor deficiency from another [7], These experiments raised the question, how the factors that cause such clear discrimina tion of patterns can be identified and how the patterns for each individual factor defi ciency are related to one another. An answer was expected from an analysis of the entire kinetics of activation.…”