Parkinson's disease is an age-related progressive neurodegenerative disorder. A large majority of Parkinson's disease patients have an unknown etiology, which is classified as idiopathic Parkinson's disease. Generating disease models directly from idiopathic Parkinson's disease patients may improve the understanding of the disease pathology. Both neuroprotective and neurodegenerative roles have been suggested for cystatin C in neurodegenerative disease. In Parkinson's disease, investigations assessing cystatin C levels in different types of biospecimens such as blood, cerebrospinal fluid, and in vitro models have had conflicting results. We present a study assessing cystatin C levels in different biospecimen types originating from the same subjects. Using a sandwich ELISA, we compared cystatin C concentration in blood derivatives (plasma and serum) and culture media of derived models (stem cells, neuroepithelial stem cells, and midbrain organoids) of three idiopathic Parkinson's disease and three age-matched healthy control subjects with the same