The chromogenic methods involve a chromogenic reagent (that induces a color reaction) of a known amount should added to the specified amount of sample incubated for the specified time. The color reaction between the investigated coagulation enzyme in the sample and the substrate starts by the addition of the reagent.
Yumizen G1500/G1550 instrument monitors this color reaction based on the change of transmitted light intensity at 405 nm (photometric). At the end of the assay the change can be obtained in absorbance per time unit using the optical curve (OD/min). The intensity of color change depends on the concentration, therefore, it requires calibration.