Patients with OND had the highest baseline age- and sex-adjusted median serum NfL (16.23 pg/mL), followed by patients with genetic PD (13.36 pg/mL), prodromal participants (12.20 pg/mL), PD patients (11.73 pg/mL), unaffected mutation carriers (11.63 pg/mL), and HCs (11.05 pg/mL); the F test of any differences among the medians had a P < 0.0001 (Fig. 1c). Here, NEFL is linked to Parkinson disease.