SLC6A3 and Parkinson disease: Considering that the olfactory test is cheap and easy to perform, although it has limitations for its low specificity, we might still screen people at high risk of developing PD with the olfactory test in combination with RBD, and then make a formal diagnosis with an examination whose specificity is high, such as dopamine transporter imaging [42] and detection of α-synuclein oligomers in cerebrospinal fluid [43], making early intervention possible.