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CSF biomarker variability in the Alzheimer's Association quality control program.

ABSTRACT: BACKGROUND:The cerebrospinal fluid (CSF) biomarkers amyloid beta 1-42, total tau, and phosphorylated tau are used increasingly for Alzheimer's disease (AD) research and patient management. However, there are large variations in biomarker measurements among and within laboratories. METHODS:Data from the first nine rounds of the Alzheimer's Association quality control program was used to define the extent and sources of analytical variability. In each round, three CSF samples prepared at the Clinical Neurochemistry Laboratory (Mölndal, Sweden) were analyzed by single-analyte enzyme-linked immunosorbent assay (ELISA), a multiplexing xMAP assay, or an immunoassay with electrochemoluminescence detection. RESULTS:A total of 84 laboratories participated. Coefficients of variation (CVs) between laboratories were around 20% to 30%; within-run CVs, less than 5% to 10%; and longitudinal within-laboratory CVs, 5% to 19%. Interestingly, longitudinal within-laboratory CV differed between biomarkers at individual laboratories, suggesting that a component of it was assay dependent. Variability between kit lots and between laboratories both had a major influence on amyloid beta 1-42 measurements, but for total tau and phosphorylated tau, between-kit lot effects were much less than between-laboratory effects. Despite the measurement variability, the between-laboratory consistency in classification of samples (using prehoc-derived cutoffs for AD) was high (>90% in 15 of 18 samples for ELISA and in 12 of 18 samples for xMAP). CONCLUSIONS:The overall variability remains too high to allow assignment of universal biomarker cutoff values for a specific intended use. Each laboratory must ensure longitudinal stability in its measurements and use internally qualified cutoff levels. Further standardization of laboratory procedures and improvement of kit performance will likely increase the usefulness of CSF AD biomarkers for researchers and clinicians.

SUBMITTER: Mattsson N

PROVIDER: S-EPMC3707386 | biostudies-literature | 2013 May

REPOSITORIES: biostudies-literature

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CSF biomarker variability in the Alzheimer's Association quality control program.

Mattsson Niklas N Andreasson Ulf U Persson Staffan S Carrillo Maria C MC Collins Steven S Chalbot Sonia S Cutler Neal N Dufour-Rainfray Diane D Fagan Anne M AM Heegaard Niels H H NH Robin Hsiung Ging-Yuek GY Hyman Bradley B Iqbal Khalid K Kaeser Stephan A SA Lachno D Richard DR Lleó Alberto A Lewczuk Piotr P Molinuevo José L JL Parchi Piero P Regeniter Axel A Rissman Robert A RA Rosenmann Hanna H Sancesario Giuseppe G Schröder Johannes J Shaw Leslie M LM Teunissen Charlotte E CE Trojanowski John Q JQ Vanderstichele Hugo H Vandijck Manu M Verbeek Marcel M MM Zetterberg Henrik H Blennow Kaj K

Alzheimer's & dementia : the journal of the Alzheimer's Association 20130501 3

<h4>Background</h4>The cerebrospinal fluid (CSF) biomarkers amyloid beta 1-42, total tau, and phosphorylated tau are used increasingly for Alzheimer's disease (AD) research and patient management. However, there are large variations in biomarker measurements among and within laboratories.<h4>Methods</h4>Data from the first nine rounds of the Alzheimer's Association quality control program was used to define the extent and sources of analytical variability. In each round, three CSF samples prepar ...[more]

PMID: 23622690

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Project description:BackgroundWe aimed to investigate the tau biomarker discrepancies of Alzheimer's disease (AD) using plasma tau phosphorylated at threonine 181 (p-tau181), cerebrospinal fluid (CSF) p-tau181, and AV1451 positron emission tomography (PET).MethodsIn the Alzheimer's Disease Neuroimaging Initiative, 724 non-demented participants were categorized into plasma/CSF and plasma/PET groups. Demographic and clinical variables, amyloid-β (Aβ) burden, flortaucipir-PET binding in Braak regions of interest (ROIs), longitudinal changes in clinical outcomes, and conversion risk were compared.ResultsAcross different tau biomarker groups, the proportion of participants with a discordant profile varied (plasma+/CSF- 15.6%, plasma-/CSF+ 15.3%, plasma+/PET- 22.4%, and plasma-/PET+ 6.1%). Within the plasma/CSF categories, we found an increase from concordant-negative to discordant to concordant-positive in the frequency of Aβ pathology or cognitive impairment, rates of cognitive decline, and risk of cognitive conversion. However, the two discordant categories (plasma+/CSF- and plasma-/CSF+) showed comparable performances, resulting in similarly reduced cognitive capacities. Regarding plasma/PET categories, as expected, PET-positive individuals had increased Aβ burden, elevated flortaucipir retention in Braak ROIs, and accelerated cognitive deterioration than concordant-negative persons. Noteworthy, discordant participants with normal PET exhibited reduced flortaucipir uptake in Braak stage ROIs and slower rates of cognitive decline, relative to those PET-positive. Therefore, individuals with PET abnormality appeared to have advanced tau pathological changes and poorer cognitive function, regardless of the plasma status. Furthermore, these results were found only in individuals with Aβ pathology.ConclusionsOur results indicate that plasma and CSF p-tau181 abnormalities associated with amyloidosis occur simultaneously in the progression of AD pathogenesis and related cognitive decline, before tau-PET turns positive.

Dataset Information

CSF biomarker variability in the Alzheimer's Association quality control program.

Publications

CSF biomarker variability in the Alzheimer's Association quality control program.

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