Abstract: Improved methods for the determination of clotting times of fibrinogen. APTT and PT are provided. Surprising and unexpected accuracy is obtained by combining a backward-looking approach to determine a desired range of values over times T1 and T2, selected in accordance with predetermined percentages of the observed Vmax, thereby avoiding early false positives due to noise and other inhomogeneities from reagent sample mixing. Thereafter, a regression analysis is performed over the time period T1 and T2 and from the derived function, the coagulation time is determined by calculating the time associated with the predetermined percentage of Vmax.