A method of determining the course of enzyme activity that is variable in time, wherein the activity is probed by conversion of a substrate of the enzyme, includes, in a selected test set up and for a determined substrate of the enzyme, determining the velocity of signal production (dFdiag/dt) resulting from a time curve of the signal (Fdiao=f(A)) obtained from splitting the substrate when it is contacted with a determined initially fixed concentration of the enzyme (E) and providing a “diagnostic plot” with the values of (dFdiag/dt) against the signal (Fdiag) and determining whether the diagnostic plot is either a straight line or a parabola and in the same test conditions, for a given test sample, determining the signal production (Fexp) resulting from splitting the substrate by the enzyme generating in and/or disappearing from the sample and providing the time curve of signal Fexp=f(t); and transforming the obtained experimental value of the signal (Fexp) into an ideal value (Ftransf).