Fig. 5.

The rate of enzyme generation (rate) for a single plasma containing controlled levels of specific coagulation factors. Immunodepleted human plasma was reconstituted at indicated coagulation factor levels and incubated with the chromogenic substrate S-2366 and thromboplastin-coated microspheres at a count of 10⁴ per mL for 3 minutes at 37°C prior to recalcification (8.3 mM, final Ca²⁺ concentration). Absorbance of light (405 nm) was recorded with a spectrometer at 1 minute intervals. Samples yielded a sigmoid relationship between absorbance and time, and the rate was recorded as the slope of the curve at which 50% of the total change in absorbance had occurred. Experiments were performed in duplicate, with the mean clotting time reported. The data points represent the mean initiation time (n=3) and the error bars represent standard error. The gray regions represent the reported range of normal coagulation factor levels.