SLC6A3 and Parkinson disease: Other strategies for pre-motor diagnosis of PD have included combining clinical features, such as olfactory loss and family history, with dopamine transporter radionuclide imaging (The Parkinson At-Risk Study or PARS), or an algorithmic approach to develop a cohort enriched with an at-risk genotype, such as LRRK2 G2019S mutation (Tolosa and Pont-Sunyer, 2011; Foroud et al., 2015).