Figure 2: The high reproducibility of the EPR measurements is well demonstrated by the plots displayed in the figure showing the calculated EPR signal levels versus the elapsed time. Two tests were performed from a healthy subject taking 6 hours from each other. The best fitting straight lines ( = 0.99) were found almost superimposable: about the 0.5% discrepancy in the ROS absolute production rate (μmol · min−1) was calculated between the measurements. The stacked plot of the recorded EPR spectra during a single experiment is displayed at the upper left corner. The spectra are centered at g = 1.997. For each spectrum, the greatest signal amplitude difference in the triplet (arbitrary units) is returned by the acquisition routine, resulting in a point of the displayed graph. The ROS production rate (arbitrary units) is estimated by the best fitting line. It can be, in turn, converted in the absolute ROS production rate level (μmol · min−1) throughout the acquisition of a stable radical compound like CP•.