Predictive probability (PP) for PD in early PD subjects compared to advanced PD, AD and healthy control groups. a) The distribution of the PP values of the early/mild PD, advanced PD, AD and healthy cohorts derived from the logistic regression analysis are depicted. The box plots represent 50% of the cases, with the median (horizontal bold line) and the 1st and 3rd quartile values (bottom and top of the box, respectively). The bottom and top whiskers show the lowest and the highest datum within 1.5x interquartile range (IQR, the range between the 1st and 3rd quartile) from bottom and top of the box, respectively. Outliers are denoted by black dots. Beyond the cut-off of PP = 0.5 the subjects were considered as having PD. b) The performance of the classifier across the entire data set. Blood samples are ordered by their PP for PD. 86 out of 93 individuals that ranked in the upper panel (>0.5) are PD. 86 out of 92 individuals that ranked in the lower panel (< 0.5) are controls. PD = Parkinson’s disease. AD = Alzheimer’s disease.