Receiver-operator characteristics (ROC) curves (A) and scatter gram (B) of the nocturnal heart rate variability parameter SDNN, evaluated from Holter recording of 22 female patients with fibromyalgia and 22 matched healthy controls. The best cut-off point (indicated by symbol 'x' in Figure 1-A was determined according to the shortest orthogonal distance from each point to the optimum value (0,1). The line in figure 1-B indicates the cut-off point (114 milliseconds (ms). SDNN, standard deviation of the NN intervals.
Lerma et al. Arthritis Research & Therapy 2011 13:R185 doi:10.1186/ar3513