VGF and Parkinson disease: When CSF samples were analyzed from two independent cohorts of subjects (n = 196) and a longitudinal cohort (n = 105), including all the controls and treated PD patients (with disease duration of no more than 6 years), the C-terminal region of the VGF protein was found to be decreased by liquid chromatography–tandem mass spectrometry in the data-independent acquisition mode [104].