Objective: This study compares tear fluid proteome in patients with idiopathic Parkinson´s disease (PD) and age-matched healthy controls (HC) to characterize disease-related proteomic changes and identify possible biomarkers for the diagnosis of PD.

Background: The diagnosis of PD is still based on purely clinical features, and it can be particularly challenging to make a correct early diagnosis and differentiate PD from atypical PD. Body fluid-derived biomarkers have become an indispensable tool in today’s clinical routine for many disorders. In PD there is no body fluid-derived biomarker established until today. The close spatial relation of the lacrimal glands to the cranial nerves and the recent reports of PD-specific changes in salivary glands may predispose tear fluid to mirror pathophysiological changes in the central nervous system and argue for a validation in clinical studies.

Methods: In 2013, we started a currently ongoing monocentric and prospective observational study, where tear fluid of patients with idiopathic PD, atypical PD as well as HC is collected using Schirmer tear test ophthalmic strips. Next to a thorough clinical characterization, additional diagnostics like transcranial ultrasound of the substantia nigra, measurements of nerve conduction velocity, cognitive function assessment, and olfactory testing are performed. The tear fluid is analyzed by mass spectrometry techniques. Proteomic data will be correlated with the diagnostic findings to identify a PD-specific biomarker profile.

Results: Tear fluid from thirty-eight patients with idiopathic PD and twenty-two HC has been collected. Test runs confirming the feasibility of protein extraction and proteomic analysis have been performed and the proteomic analysis is currently ongoing.

Conclusions: We have demonstrated that tear fluid is an easily accessible body fluid and that its collection is non-invasive and painless to the patient. In addition, it is a relative pure body fluid and can therefore be collected without contaminations, that could confound the evaluation of relevant protein levels. Furthermore, tear fluid has already been intensively studied in other diseases and therefore sample collection, processing and analytic techniques have been widely validated. Our study has thus the potential to identify a tear fluid-based biomarker constellation, which could facilitate the diagnosis and differential diagnosis of PD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/tear-fluid-as-potential-biomarker-for-the-diagnosis-of-parkinsons-disease/