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P1–184: Comparison of surrogate matrix and surrogate analyte approaches for quantifying beta‐amyloid peptides in human cerebrospinal fluid using LC‐MS/MS methods
Author(s) -
Jenkins Rand,
Mylott William,
Yuan Moucun,
Shao Junlong,
Hidy Bruce
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.2013.05.407
Subject(s) - analyte , chemistry , chromatography , matrix (chemical analysis)
Background: CSF Ab1-42, T-tau and P-tau are finding increasing considered as biomarkers of Alzheimer’s disease (AD) and are incorporated in new diagnostic criteria. Critical to their utility is to understand and to reduce potential confounding factors in their measurement, in particular the problem of Ab1-42 adsorption. This study aimed to determinewhether measured CSF concentrations of each biomarker are affected by the aliquot storage volume; and whether addition of a mild detergent-containing buffer would mitigate any observed effects. Methods: Pooled AD and control CSF was distributed into polypropylene tubes [Sarstedt 72.694.406] in triplicate in aliquots of 8 different volumes (50 to 1500 uL) and freeze thawed. Ab1-42 and T-tau were measured on a Meso Scale Discovery 6000 platform and P-tau using an ELISA assay. For each aliquot volume samples were measured twice (Rounds 1 and 2), and again following addition of Tween 20 [0.05%). To discount any effects of pooling, the experiment was also conducted on CSF from an individual subject and stored in Fisherbrand tubes (FB74031). Relationship between CSF biomarker levels and volume were assessed using regression analyses. Results: In both Rounds 1 and 2 measured concentrations of A b142 significantly increased with aliquot storage volume, approximately doublingwith an aliquot increase from 50 to 1500uL (Figure 1). Thus in Round 1 a CSF aliquot increase of 10mL predicted an A b142 increase of 0.98pg/ml (95%CI 0.21 1.76 p 1⁄40.02) in controls, and 1.16pg/ml (95%CI 0.63 1.68, p 1⁄40.002) in AD. Following addition of Tween, the positive relationship between A b142 and aliquot volume was no longer present (Figure 1D). There was no association between Ttau or P-Tau concentration and aliquot volume in AD or control pooled CSF samples, or the individual sample. Conclusions: The aliquot volume in which CSF is stored has a clinically and statistically significant impact on the measured concentration of Ab1-42, but not T-tau nor P-tau, with potentially important diagnostic and research implications. These findings may be at least partially explained by adsorption of Ab1-42 to storage vessel walls; introduction of a buffer detergent at initial aliquoting stage may be an effective solution to this problem.