biostudies-literatureUnknown21(18)Klafki HWThe ratio of amyloid precursor protein (APP)669-711 (Aβ-3-40)/Aβ1-42 in blood plasma was reported to represent a novel Alzheimer's disease biomarker. Here, we describe the characterization of two antibodies against the N-terminus of Aβ-3-x and the development and "fit-for-purpose" technical validation of a sandwich immunoassay for the measurement of Aβ-3-40. Antibody selectivity was assessed by capillary isoelectric focusing immunoassay, Western blot analysis, and immunohistochemistry. The analytical validation addressed assay range, repeatability, specificity, between-run variability, impact of pre-analytical sample handling procedures, assay interference, and analytical spike recoveries. Blood plasma was analyzed after Aβ immunoprecipitation by a two-step immunoassay procedure. Both monoInternational journal of molecular sciencesE6564https://www.ebi.ac.uk/biostudies/studies/S-EPMC7555726biostudies-literatureDevelopment and Technical Validation of an Immunoassay for the Detection of APP669-711 (Aβ-3-40) in Biological Samples.PMC7555726Klafki HWBeyer IJahn OKnolker HJVogelgsang JWiltfang JMatzen AZampar SRohdenburg LOberstein TJLachmann IRieper PWirths OOsterloh DfalseDevelopment and Technical Validation of an Immunoassay for the Detection of APP669-711 (Aβ-3-40) in Biological Samples.The ratio of amyloid precursor protein (APP)669-711 (Aβ-3-40)/Aβ1-42 in blood plasma was reported to represent a novel Alzheimer's disease biomarker. Here, we describe the characterization of two antibodies against the N-terminus of Aβ-3-x and the development and "fit-for-purpose" technical validation of a sandwich immunoassay for the measurement of Aβ-3-40. Antibody selectivity was assessed by capillary isoelectric focusing immunoassay, Western blot analysis, and immunohistochemistry. The analytical validation addressed assay range, repeatability, specificity, between-run variability, impact of pre-analytical sample handling procedures, assay interference, and analytical spike recoveries. Blood plasma was analyzed after Aβ immunoprecipitation by a two-step immunoassay procedure. Both mono2020-01-01T00:00:00Z2020 Sep2025-04-06T12:18:55.912Z2020-10-29T10:51:11ZS-EPMC75557263291170610.3390/ijms21186564