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P1–170: Evaluation of pre‐analytical and analytical factors that contribute to variability in CSF biomarker levels
Author(s) -
Shah Aarti,
Sutphen Courtney,
Amos Matthew,
Althage Matthew,
Morris John,
Holtzman David,
Fagan Anne
Publication year - 2013
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1016/j.jalz.2013.05.393
Subject(s) - biomarker , analyte , disease , medicine , oncology , statistics , chromatography , mathematics , chemistry , biology , genetics
development for tau that shows a marked improvement in precision, linearity and reproducibility when compared to currently available tests. Methods: An in vitro diagnostic test for tau is being developed for the VITROS Immunodiagnostic Systems, and analytical performance was evaluated following CLSI guidelines using two VITROS Tau assay reagent lots, 3 CSF pools, and 3 controls. Linearity was tested with 11 admixtures of endogenous tau in CSF and recombinant tau 441 in buffer. Interference testing included commonly prescribed drugs, recombinant tau, Ab peptides, and endogenous substances. Limit of detection (LoD) and lower limit of quantitation were confirmed with 20 replicates per day on 3 days. Results: The median within-laboratory coefficient of variation (CV) for the 3 CSF pools was 3.3% with a range of 2.4% 4.2%. The controls’ within-laboratory CV was 1.2%. Repeatability CVs were 1.9% for CSF pools and 1.2% for controls. The assay showed good linearity across themeasuring range (08,000pg/mL) with the admixture of endogenous and synthetic peptide. Bias introduced by commonly prescribed drugs at high levels was <610%. The interference from Ab peptides at greater than known physiological concentrations as well as from endogenous substances was <5%. The limit of detection was 9.5pg/mL; the lower limit of quantitation was 40pg/mL. Conclusions: VITROS Immunodiagnostic Products Tau Assay 1 demonstrates excellent analytical performance: it is precise, linear and the tested interferences cause no significant bias. The fully automated format and ability to perform these assays in a clinical laboratory should make testing for these important markers more reliable and routine.