Gene expression profiling of peripheral blood leukocytes identifies and validates ABCB1 as a novel biomarker for Alzheimer's disease

► Relatively high success rate (72%) in validation by using pathway-based gene selection. ► Strong association of the ABC transporter category with MCI and AD was observed. ► The expression levels of ABCB1 were positively associated with the MMSE scores of study population. ► Our approach serves as a new way to examine molecular abnormalities in leukocytes.