{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,10]],"date-time":"2026-02-10T16:37:45Z","timestamp":1770741465605,"version":"3.49.0"},"reference-count":37,"publisher":"MDPI AG","issue":"18","license":[{"start":{"date-parts":[[2020,9,8]],"date-time":"2020-09-08T00:00:00Z","timestamp":1599523200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>The ratio of amyloid precursor protein (APP)669\u2013711 (A\u03b2\u22123\u201340)\/A\u03b21\u201342 in blood plasma was reported to represent a novel Alzheimer\u2019s disease biomarker. Here, we describe the characterization of two antibodies against the N-terminus of A\u03b2\u22123\u2013x and the development and \u201cfit-for-purpose\u201d technical validation of a sandwich immunoassay for the measurement of A\u03b2\u22123\u201340. 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 A\u03b2 immunoprecipitation by a two-step immunoassay procedure. Both monoclonal antibodies detected A\u03b2\u22123\u201340 with no appreciable cross reactivity with A\u03b21\u201340 or N-terminally truncated A\u03b2 variants. However, the amyloid precursor protein was also recognized. The immunoassay showed high selectivity for A\u03b2\u22123\u201340 with a quantitative assay range of 22 pg\/mL\u20137.5 ng\/mL. Acceptable intermediate imprecision of the complete two-step immunoassay was reached after normalization. In a small clinical sample, the measured A\u03b242\/A\u03b2\u22123\u201340 and A\u03b242\/A\u03b240 ratios were lower in patients with dementia of the Alzheimer\u2019s type than in other dementias. In summary, the methodological groundwork for further optimization and future studies addressing the A\u03b242\/A\u03b2\u22123\u201340 ratio as a novel biomarker candidate for Alzheimer\u2019s disease has been set.<\/jats:p>","DOI":"10.3390\/ijms21186564","type":"journal-article","created":{"date-parts":[[2020,9,8]],"date-time":"2020-09-08T09:03:48Z","timestamp":1599555828000},"page":"6564","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":18,"title":["Development and Technical Validation of an Immunoassay for the Detection of APP669\u2013711 (A\u03b2\u22123\u201340) in Biological Samples"],"prefix":"10.3390","volume":"21","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-8672-9032","authenticated-orcid":false,"given":"Hans W.","family":"Klafki","sequence":"first","affiliation":[{"name":"Department of Psychiatry and Psychotherapy, University Medical Center (UMG), Georg-August-University, D37075 G\u00f6ttingen, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Petra","family":"Rieper","sequence":"additional","affiliation":[{"name":"Department of Psychiatry and Psychotherapy, University Medical Center (UMG), Georg-August-University, D37075 G\u00f6ttingen, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Anja","family":"Matzen","sequence":"additional","affiliation":[{"name":"IBL International GmbH, Tecan Group Company, D-22335 Hamburg, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0134-0974","authenticated-orcid":false,"given":"Silvia","family":"Zampar","sequence":"additional","affiliation":[{"name":"Department of Psychiatry and Psychotherapy, University Medical Center (UMG), Georg-August-University, D37075 G\u00f6ttingen, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4115-0334","authenticated-orcid":false,"given":"Oliver","family":"Wirths","sequence":"additional","affiliation":[{"name":"Department of Psychiatry and Psychotherapy, University Medical Center (UMG), Georg-August-University, D37075 G\u00f6ttingen, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9326-8193","authenticated-orcid":false,"given":"Jonathan","family":"Vogelgsang","sequence":"additional","affiliation":[{"name":"Department of Psychiatry and Psychotherapy, University Medical Center (UMG), Georg-August-University, D37075 G\u00f6ttingen, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Dirk","family":"Osterloh","sequence":"additional","affiliation":[{"name":"Roboscreen GmbH, D-04129 Leipzig, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Lara","family":"Rohdenburg","sequence":"additional","affiliation":[{"name":"Department of Psychiatry and Psychotherapy, University Medical Center (UMG), Georg-August-University, D37075 G\u00f6ttingen, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4369-6875","authenticated-orcid":false,"given":"Timo J.","family":"Oberstein","sequence":"additional","affiliation":[{"name":"Department of Psychiatry and Psychotherapy, Friedrich-Alexander-University of Erlangen-Nuremberg, D-91054 Erlangen, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3397-8924","authenticated-orcid":false,"given":"Olaf","family":"Jahn","sequence":"additional","affiliation":[{"name":"Max-Planck-Institute of Experimental Medicine, Proteomics Group, D-37075 G\u00f6ttingen, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Isaak","family":"Beyer","sequence":"additional","affiliation":[{"name":"Faculty of Chemistry, Technische Universit\u00e4t Dresden, D-01069 Dresden, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ingolf","family":"Lachmann","sequence":"additional","affiliation":[{"name":"Roboscreen GmbH, D-04129 Leipzig, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9631-5239","authenticated-orcid":false,"given":"Hans-Joachim","family":"Kn\u00f6lker","sequence":"additional","affiliation":[{"name":"Faculty of Chemistry, Technische Universit\u00e4t Dresden, D-01069 Dresden, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1492-5330","authenticated-orcid":false,"given":"Jens","family":"Wiltfang","sequence":"additional","affiliation":[{"name":"Department of Psychiatry and Psychotherapy, University Medical Center (UMG), Georg-August-University, D37075 G\u00f6ttingen, Germany"},{"name":"German Center for Neurodegenerative Diseases (DZNE), D-37075 G\u00f6ttingen, Germany"},{"name":"Neurosciences and Signaling Group, Institute of Biomedicine (iBiMED), Department of Medical Sciences, University of Aveiro, 3810-193 Aveiro, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2020,9,8]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"59","DOI":"10.1111\/ene.13439","article-title":"Alzheimer\u2019s disease","volume":"25","author":"Lane","year":"2018","journal-title":"Eur. 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