LRRK2 and Parkinson disease: To investigate the central question of whether our assay can stratify PD patients with elevated LRRK2 activity in clinical trials, we analyzed Rab10-pThr73 levels in neutrophils of four LRRK2-G2019S carriers with PD, together with an equal number of healthy controls in a blinded experimental setup (see Experimental Procedures, supplemental Table S4).