Short-interval variability and test-retest reliability of Alzheimer’s disease plasma biomarkers in a clinically heterogenous cohort
12 affiliations
- 1Dementia Research Centre, Department of Neurodegenerative Disease, UCL Queen Square Institute of Neurology, University College London, London, WC1N 3AR UK
- 2UK Dementia Research Institute at UCL, University College London, London, UK
- 3Neurology Department, Royal Adelaide Hospital and Queen Elizabeth Hospital, Adelaide, Australia
- 4School of Medicine, Adelaide University, Adelaide, Australia
- 5Neuroimmunology & CSF Laboratory, National Hospital for Neurology and Neurosurgery, Queen Square, London, UK
- 6Department of Neuroinflammation, UCL Queen Square Institute of Neurology, London, UK
- 7MRC Centre for Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
- 8Department of Psychiatry and Neurochemistry, Institute of Neuroscience and Physiology, the Sahlgrenska Academy at the University of Gothenburg, Mölndal, Sweden
- 9Clinical Neurochemistry Laboratory, Sahlgrenska University Hospital, Mölndal, Sweden
- 10Department of Pathology and Laboratory Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI USA
- 11Wisconsin Alzheimer’s Disease Research Center, University of Wisconsin School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI USA
- 12Centre for Brain Research, Indian Institute of Science, Bangalore, India
Abstract
Background: Assessment of short-term within-subject variability and test-retest reliability of Alzheimer’s disease (AD)-related plasma biomarkers is important for real-world clinical implementation and interpretation in research studies. In this study we aimed to assess short-term variability and reliability of core AD plasma biomarkers, proposed ratios, and evaluate a broader proteomic panel.
Methods: Two serial plasma samples were collected from each of the 92 participants enrolled in observational research studies over intervals ranging from 30 minutes to three months. Test-retest reliability and within-subject variability were assessed for 131 biomarkers measured on three immunoassays (Lumipulse G plasma p-tau217; Fujirebio, NULISAseq CNS Disease Panel and NULISAqpcr AD 5-Plex; Alamar Biosciences). We subsequently evaluated the stability of a dual cut-point approach for AD probability diagnostic categorisation and examined whether within-subject variability was associated with inter-sample interval (time between serial blood sampling).
Results: All core AD plasma biomarkers assessed in this study (Aβ42, BD-p-tau181, BD-p-tau217, BD-p-tau231, p-tau181, p-tau217, p-tau231, GFAP and NfL) demonstrated strong correlations (r ≥ 0.79) and high reliability (ICC ≥ 0.84). Within-subject variability was moderate to low for core AD plasma biomarkers. Using a validated dual cut-point approach for plasma p-tau217, most individuals (92%) remained within the same diagnostic category (high/indeterminate/low) across both timepoints, and no individual moved across two boundaries (i.e. from high to low AD probability categorisation or vice versa). For the majority of analytes, within-subject variability was not associated with inter-sample interval after adjustment for age and sex, however, the core AD plasma biomarker, NfL did have a significant association.
Conclusions: While core AD plasma biomarkers had limited variability and high reliability over short-intervals, other central nervous system (CNS)-relevant biomarkers showed greater variability, which may be relevant for interpretation in association studies and clinical applications.
Supplementary Information: The online version contains supplementary material available at https://doi.org/10.1186/s13195-026-02180-8.
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BibTeX
@article{beament2026shortinterval,
title = {{Short-interval variability and test-retest reliability of Alzheimer’s disease plasma biomarkers in a clinically heterogenous cohort}},
author = {Millie Beament and Katharine Wiltshire and Christopher R S Belder and Emily Abel and Melanie Hart and Amanda J Heslegrave and Michael P Lunn and Miguel Rosa-Grilo and Owen Swann and Jonathan M Schott and Henrik Zetterberg and Nick C Fox and Ashvini Keshavan},
journal = {Alzheimer's Research \& Therapy},
year = {2026},
month = oct,
doi = {10.1186/s13195-026-02180-8},
url = {https://doi.org/10.1186/s13195-026-02180-8},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Short-interval variability and test-retest reliability of Alzheimer’s disease plasma biomarkers in a clinically heterogenous cohort
AU - Millie Beament
AU - Katharine Wiltshire
AU - Christopher R S Belder
AU - Emily Abel
AU - Melanie Hart
AU - Amanda J Heslegrave
AU - Michael P Lunn
AU - Miguel Rosa-Grilo
AU - Owen Swann
AU - Jonathan M Schott
AU - Henrik Zetterberg
AU - Nick C Fox
AU - Ashvini Keshavan
PY - 2026
DA - 2026/10/27
JO - Alzheimer's Research & Therapy
DO - 10.1186/s13195-026-02180-8
UR - https://doi.org/10.1186/s13195-026-02180-8
AB - Background: Assessment of short-term within-subject variability and test-retest reliability of Alzheimer’s disease (AD)-related plasma biomarkers is important for real-world clinical implementation and interpretation in research studies. In this study we aimed to assess short-term variability and reliability of core AD plasma biomarkers, proposed ratios, and evaluate a broader proteomic panel. Methods: Two serial plasma samples were collected from each of the 92 participants enrolled in observational research studies over intervals ranging from 30 minutes to three months. Test-retest reliability and within-subject variability were assessed for 131 biomarkers measured on three immunoassays (Lumipulse G plasma p-tau217; Fujirebio, NULISAseq CNS Disease Panel and NULISAqpcr AD 5-Plex; Alamar Biosciences). We subsequently evaluated the stability of a dual cut-point approach for AD probability diagnostic categorisation and examined whether within-subject variability was associated with inter-sample interval (time between serial blood sampling). Results: All core AD plasma biomarkers assessed in this study (Aβ42, BD-p-tau181, BD-p-tau217, BD-p-tau231, p-tau181, p-tau217, p-tau231, GFAP and NfL) demonstrated strong correlations (r ≥ 0.79) and high reliability (ICC ≥ 0.84). Within-subject variability was moderate to low for core AD plasma biomarkers. Using a validated dual cut-point approach for plasma p-tau217, most individuals (92%) remained within the same diagnostic category (high/indeterminate/low) across both timepoints, and no individual moved across two boundaries (i.e. from high to low AD probability categorisation or vice versa). For the majority of analytes, within-subject variability was not associated with inter-sample interval after adjustment for age and sex, however, the core AD plasma biomarker, NfL did have a significant association. Conclusions: While core AD plasma biomarkers had limited variability and high reliability over short-intervals, other central nervous system (CNS)-relevant biomarkers showed greater variability, which may be relevant for interpretation in association studies and clinical applications. Supplementary Information: The online version contains supplementary material available at https://doi.org/10.1186/s13195-026-02180-8.
SN - 1758-9193
ER -