The TearAD Study: Tear Biomarkers for Alzheimer's Disease (AD) Screening and Diagnosis

Study Overview
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Brief Summary
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The goal of this observational longitudinal study is to investigates whether tear fluid is a non-invasive source of biomarkers for Alzheimer's disease. The main aim of the study is to evaluate diagnostic accuracy measures (sensitivity and specificity) of tear and retinal biomarkers to discriminate individuals with and without neurodegeneration. Tear fluid from participants will be collected non-invasively with Schirmer's strips, which is a small paper strip placed in the lower eye lid for a maximum of 5 minutes. Additionally, standard, ultra-wide field and cross-sectional retinal images will be obtained.

Official Title
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The TearAD Study: Tear Biomarkers for Alzheimer's Disease (AD) Screening and Diagnosis

Conditions
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Alzheimer Disease

Intervention / Treatment
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* Diagnostic Test: Tear Fluid collection (Schirmer's strip)
* Diagnostic Test: Retinal imaging


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria (healthy controls): Available CSF, PET, CT or MRI data to evaluate the presence/absence of neurodegeneration (preferably within 1 year of inclusion in this study) Absence of cognitive complaints or treatment and did not seek help for cognitive complaints in the past MMSE score 26-30 at baseline Age > 50 years Available for follow-up (up to 24 months) Written informed consent obtained and documented Inclusion criteria (patients): Available CSF, PET, CT or MRI data to evaluate the presence/absence of neurodegeneration (preferably within 1 year of inclusion in this study) Available for follow-up (up to 24 months) Written informed consent obtained and documented Capable of giving informed consent themselves (MMSE score > 17/30) Exclusion Criteria (all subjects): Ocular conditions that could influence tear biochemical parameters (including eye infection, eye inflammation, eye surgery within the last 28 days or other acute eye conditions) Neurological or systemic chronic conditions known to interfere with retinal thickness (e.g., glaucoma, diabetes mellitus) Ocular conditions interfering with optical coherence tomography (OCT) quality/retinal thickness: e.g. severe cataract, age-related macular degeneration, and glaucoma

Ages Eligible for Study
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Minimum Age: 50 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| With Neurodegeneration<br>Includes patients with mild cognitive impairment and dementia | Diagnostic Test: Tear Fluid collection (Schirmer's strip)<br>* Tear fluid will be collected non-invasively form all participants with the use of Schirmer's strips, which is a small paper strip placed in the lower eye lid for a maximum of 5 minutes.<br>Diagnostic Test: Retinal imaging<br>* The retina from all participants will be visualised with the use of a standard (Clarus 700 Zeiss), ultra-wide field (Optos), and cross-sectional (Optical Coherence Tomography) retinal images.<br>|
| Without Neurodegeneration<br>Includes healthy controls and patients with subjective cognitive decline | Diagnostic Test: Tear Fluid collection (Schirmer's strip)<br>* Tear fluid will be collected non-invasively form all participants with the use of Schirmer's strips, which is a small paper strip placed in the lower eye lid for a maximum of 5 minutes.<br>Diagnostic Test: Retinal imaging<br>* The retina from all participants will be visualised with the use of a standard (Clarus 700 Zeiss), ultra-wide field (Optos), and cross-sectional (Optical Coherence Tomography) retinal images.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Capability of tear biomarkers to discriminate individuals with neurodegeneration from those without neurodegeneration and assess the change in biomarker levels over time. | Levels of tear biomarkers will be determined from the Schirmer's strips. The biomarker levels will be analysed to see whether they can be discriminate between people with and without neurodegeneration. | Sampling done at t= 0, 1 and 2 years. | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| The difference in tear biomarker level between patients and controls, and between patient groups and how these differences change over time. | Additional analysis to see whether tear biomarkers can also discriminate patients from controls and differences inbetween patient groups. | Sampling done at t= 0, 1 and 2 years. | 
| Correlation of biomarker levels in tears, blood and cerebral spinal fluid (CSF). | This analysis will be done to determine the correlation between biomarkers of different body fluids. | Baseline measurements (t=0) will be used to determine correlation. | 
| Correlation between tear biomarkers and other ocular imaging biomarkers, as well as assessing the change of this correlation over time. | The correlation between tear biomarkers and ocular imaging biomarkers (e.g. thickness of the retinal nerve fiber layer, retinal vasculature tortuosity) will be analysed. | Imaging done at t= 0, 1 and 2 years. | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Tear Fluid, Retinal imaging, Biomarkers