Furthermore, results of the comparison of the CSFasynSAA− LRRK2 parkinsonism group with the CSFasynSAA+ sPD group must be interpreted with caution as the inclusion criteria pertaining to disease duration and treatment status at enrolment differed substantially for the sPD and LRRK2 parkinsonism cases enrolled in PPMI and were not fully accounted for by frequency matching of the sPD group to the LRRK2 group as a whole. Here, LRRK2 is linked to Parkinson disease.