Derivation of cutoffs for the Elecsys ® amyloid β (1–42) assay in Alzheimer's disease

Leslie M. Shaw, Teresa Waligorska, Leona Fields, Magdalena Korecka, Michal Figurski, John Q. Trojanowski, Udo Eichenlaub, Simone Wahl, Marian Quan, Michael J. Pontecorvo, D. Richard Lachno, Jayne A. Talbot (+3 others)
2018 Alzheimer's and Dementia: Diagnosis, Assessment and Disease Monitoring  
An Elecsys® Amyloid β (Aβ [1-42]) immunoassay cutoff for classification of patients with Alzheimer's disease was investigated. Cerebrospinal fluid samples collected from patients with mild-to-moderate Alzheimer's disease were analyzed by Elecsys® immunoassays: (1) Aβ (1-42), (2) total tau, and (3) phosphorylated tau. Cutoffs (Aβ [1-42] and ratios with tau) were estimated by method comparison between AlzBio3 (n = 206), mixture modeling (n = 216), and concordance with florbetapir F 18
more » ... d classification (n = 75). A 1065-pg/mL (95% confidence interval: 985-1153) Elecsys® Aβ (1-42) cutoff provided 94% overall percentage agreement with AlzBio3. Comparable cutoff estimates (95% confidence interval) were derived from mixture modeling (equally weighted: 1017 [949-1205] pg/mL; prevalence weighted: 1172 [1081-1344] pg/mL) and concordance with florbetapir F 18 imaging (visual read: 1198 [998-1591] pg/mL; automated: 1198 [1051-1638] pg/mL). Based on three approaches, a 1100-pg/mL Elecsys® Aβ (1-42) cutoff is suitable for clinical trials with similar populations and preanalytical handling.
doi:10.1016/j.dadm.2018.07.002 pmid:30426066 pmcid:PMC6222032 fatcat:vekmnjwenvc2bcc7um2hwjpnme