TSPO and Alzheimer disease: Direct comparisons of medium and high affinity binding status, as determined by the TSPO SNP, did not show any significant differences of TSPO-PET z-scores in females and males with AD (Additional file 1: Table S1), fitting to our previous observation of similar [18F]GE-180 TSPO-PET signals between subjects with medium and high affinity binding status [33].