This a study to improve diagnosis of dementia with Lewy bodies with RT-QuIC in different biospecimens.

Background. The number of persons living with dementia is increasing in Denmark and worldwide because the population is generally growing older. Dementia with Lewy bodies (DLB) is the second most prevalent etiology among the neurodegenerative diseases that give rise to dementia.

DLB is characterized by many prodromal symptoms years before dementia is evident. Currently, little is known about the course of symptoms in the prodromal phase, and furthermore, the diagnosis of DLB can be clinically challenging, especially in the early stages. A novel technique for the measurement of misfolded alpha-synuclein (aSyn) is Real-Time Quaking-Induced Conversion (RT-QuIC), which may be able to support the diagnostic process.

Objective: Determining which biospecimen alone or in conjunction with other biospecimens can most accurately discriminate patients with DLB from Alzheimer's disease (AD) assessed by RT-QuIC for aSyn.

Design: Cross-sectional case-control study of the diagnostic accuracy of pathological alpha-synuclein assessed by RT-QuIC in different biospecimens (CSF, skin, olfactory mucosa, saliva, feces, and urine) from patients with DLB versus AD.

Patients will also be scored with tests for cognitive function, dysautonomia, and movement disorders.

Inclusion criteria for healthy controls (HC):

• Age 18 - 40 years of age
• Able to cooperate as evaluated by the primary investigator (PI)
• Able to give informed consent

Exclusion criteria

• Signs of neurological/psychiatric conditions
• Known genetic neurodegenerative disease in close family

Inclusion criteria for patients with Dementia with Lewy Bodies (DLB):

• Probable DLB (McKeith et al., 2017) or MCI-LB (McKeith et al., 2020)
• Age > 50 years of age
• Able to give informed consent
• Able to cooperate as evaluated by the PI
• MCI, mild or moderate dementia, and MMSE > 18

Exclusion criteria for patients with DLB:

• Patients not able to give informed consent.
• Current alcohol or drug abuse
• Terminal illness
• Diagnosed with major neurological/psychiatric conditions other than DLB.

Inclusion criteria for controls (patients with Alzheimer's disease (AD)):

• Probable AD (McKhann et al., 2011) or MCI-AD (Albert et al., 2011)
• Age > 50 years of age
• Able to give informed consent
• Able to cooperate as evaluated by the PI
• MCI, mild or moderate dementia, and MMSE > 18

Exclusion criteria for controls (patients with AD):

• Patients not able to give consent.
• Current alcohol or drug abuse
• Terminal illness
• Diagnosed with major neurological/psychiatric conditions other than AD.

Twenty-five patients with probable DLB or mild cognitive impairment with Lewy bodies (MCI-LB) and 25 patients with AD or MCI-AD controls will be included from the memory clinic.