Methods

Table 1. Overview of baseline assessments

Clinical Evaluation and Cognition

Assessment of the clinical impact of using blood-based biomarkers (BBMs)

We document detailed information on diagnosis, certainty of diagnosis, patient management plans (including additional examinations, referrals, etc.), and changes in treatment after each step in the diagnostic process. The steps are as follows: step-1: care-as-usual without AD biomarkers; step-2: addition of plasma AD biomarkers; and step-3: addition of advanced work-up using a CSF/PET AD biomarker. Through this process, we determine how the implementation of plasma biomarkers might improve diagnosis and management when no other AD biomarker is available, and also whether the results from plasma AD biomarkers yield diagnostic accuracy, certainty of diagnosis, and patient care that are comparable to more expensive and invasive CSF/PET biomarkers.

Cognitive testing

The cognitive battery is outlined in the table above. Attention and executive function are assessed using the Trail Making Test A and B (TMT), the Symbol Digit Modalities Test (SDMT), and the Quick Test of Cognitive Speed (AQT). Visuospatial ability is measured using two subtests from the Visual Objects and Space Perception (VOSP) battery: Incomplete Letters and Cube Analysis. Memory is assessed with the 10-word delayed recall test from ADAS-cog, including a recognition component. Verbal ability will be evaluated with the animal and letter S fluency tests and the 15-item short version of the Boston Naming Test. Global cognition will be assessed with the Mini-Mental State Examination (MMSE). Computerized cognitive batteries focusing on memory, attention, visuospatial ability, and navigation is also administered (an in-house developed battery – BioCog).

Assessments of symptoms and ADL

Cognitive symptoms

All subjects rate their memory and attention/executive function relative to others of the same age according to the Brief Anosognosia Scale (BAS). We have also added similar questions to cover the other cognitive domains. These questions have been validated against neuropsychological testing but there are data indicating that self-reported cognitive complaints are only valid in a lesser degree of cognitive impairment. Cognitive and associated symptpoms are assessed using the Cognitive Impairment Questionnaire (CIMP-QUEST), filled out by an informant.

Functional ability

This is evaluated with the informant-based Functional Activities Questionnaire (FAQ) focusing on instrumental activities of daily living (IADL).

Global function

Participants are classified as having SCD, MCI or dementia based on the neuropsychological battery, clinical symptoms and loss of independence in ADL.

Neuropsychiatric symptoms and Behavioral and psychological symptoms in dementia (BPSD)

Neuropsychiatric symptoms and Behavioral and Psychological Symptoms of Dementia (BPSD) are assessed using the Mild Behavioral Impairment Checklist (MBI-C). Mood and anxiety levels are further assessed using the Hospital Anxiety and Depression Scale (HADS).

Sleep

The presence of REM sleep behavior disorder will be evaluated with a single validated composite question derived from the Mayo Sleep Questionnaire. Sleep quality is also assessed using questions from the Sleep Scale from the Medical Outcomes Study (MOS).

Cognitive reserve

Premorbid cognition and cognitive reserve are estimated using the Cognitive Reserve Index questionnaire (CRI-q), specifically the subitems “Education” and “Working Activity” (excluding “Leisure Time”).

Cerebrospinal fluid (CSF) and blood sampling and analyzes

Lumbar CSF samples are collected according to a standardized protocol, adhering to the Alzheimer’s Association Flow Chart for CSF biomarkers. Lumbar punctures are performed between 8-12 am. 20 ml of CSF is collected in low binding tubes and stored on ice for 5-20 minutes before being centrifuged (2000g, +4°C, 10 min). Subsequently, the CSF is aliquoted in approximately 1 ml portions into low binding polypropylene tubes and then stored at -80°C until batch analyses.

About 0.5 ml of CSF from each individual at both baseline and follow-up is analyzed directly as part of routine clinical measurements for Aβ42, Aβ40, Tau, P-tau, and NfL using Lumipulse.

Plasma is collected during the same visit as the lumbar puncture. Blood is drawn into tubes containing either EDTA or Lithium heparin. Following centrifugation (2000g, +4°C, 10 min), plasma samples are aliquoted into low binding tubes and stored at -80°C pending biochemical analyses. Further, EDTA-blood will also be obtained for genetic DNA analyses. Plasma is sent bi-weekly to C2N Diagnostics for analysis using the PrecivityAD2 test (mass spectrometry analysis of plasma Aβ42, Aβ40, p-tau217 and non p-tau217).

Enrollment in BioFINDER-2

After the baseline assessments, a subsample of participants are enrolled in BioFINDER-2 undergoing BioFINDER-2 baseline assessments and longitudinal follow-ups as described here.