QRT-PCR assessment of the relative transcript expression levels in the marker panel. The box plots depict the natural logarithms of the relative gene expression levels (calculated by dividing the QRT-PCR values by the geometric mean of the HKs ACTB, ALAS1 and GAPDH raw quantities) for the individual five genes in blood samples of 62 early stage PD patients (Early PD; H&Y = 1.40 (SD = 0.56)), 30 PD patients at relatively advanced stage (Advanced PD; H&Y = 3.07 (SD = 0.81)), 29 AD patients and 64 healthy age-matched subjects (Control). Outliers are denoted by black dots. The significance was calculated by one-way ANOVA, with post-Hoc Tukey analysis. *p<0.05 vs control; ~p<0.05 vs early PD. In the text, expression level changes (percentage) refer to relative gene expression levels and not to the natural logarithms.