Reference interval and the role of plasma oligomeric beta amyloid in screening of risk groups for cognitive dysfunction at health checkups.

BACKGROUND Alzheimer's disease (AD) has a prolonged preclinical stage characterized by cognitive dysfunction. Simple, reliable, and noninvasive biomarkers reflecting the pathogenesis of AD are needed for screening cognitive dysfunction in primary health care. The aims of this study were to determine (1) the potential utility of the Multimer Detection System-Oligomeric Amyloid-β (MDS-OAβ) value in cognitive assessments and (2) the reference interval (RI) of plasma MDS-OAβ values in the general population. METHODS This prospective study consecutively recruited 1,594 participants who underwent health checkups including cognitive function examination at 16 health-promotion centers in Korea between December 2020 and January 2021. The inBloodTM OAβ test (PeopleBio, Gyeonggi-do, Republic of Korea) was utilized to quantify MDS-OAβ values in plasma. The reference subjects were obtained among those with normal general cognition on cognitive screening tools. RIs were established according to the CLSI C28-A3 guidelines. RESULTS The median MDS-OAβ value was higher in subjects with Korean Dementia Screening Questionnaire-Cognition (KDSQ-C) scores ≥8 than in those with KDSQ-C scores of 6-7 (P = 0.013). The median MDS-OAβ value was higher in subjects with Mini-Mental State Examination for Dementia Screening (MMSE-DS) scores of 21-26 than in those with MMSE-DS scores ≥27 (P = 0.011). The RI (one-side upper 95th percentile) of the MDS-OAβ value was 0.80 ng/mL (95% confidence interval = 0.78-0.82) in those aged ≥50 years. CONCLUSIONS The plasma MDS-OAβ value reflects cognitive function as assessed using the KDSQ-C and MMSE-DS. RIs obtained from a large and cognitively healthy community-based sample are presented.