P2‐062: Evaluation of beta amyloid loss to CSF sample collection and storage containers
Henry Riordan, Yoka Thomas, Neal R. Cutler, Mark T. Leibowitz, Kathryn S. Rogers, Kathryn Dawson, Michele Malone, Steve E. Unger, William L. Nowatzke · Alzheimer s & Dementia · 2011
The accurate quantification of CSF biomarkers is paramount in the development of AD drugs but measurement has varied due to handling and storage material characteristics. The purpose of this study was to systematically evaluate an assortment of CSF collection/storage materials in hopes of identifying those associated with the least amount of CSF beta amyloid (Aß) loss. Nine separate types of collection/storage tubes were compared to an alliquotted control pipetted directly from the source polypropylene conical vial for three isoforms of Aß (38, 40, 42). Coefficient of variations determined sample accuracy based on two collections corresponding to regular Rainin pipet tips and Rainin Low-Retention pipet tips. Additionally, two common long tubing types (Tygon and Silastic) were compared across various cumulative CSF quantities of 2, 4, 6, 8, 10 and 12 mLs. Grand mean differences in storage/collection tubes were evident (- 28.4, -29.4 and -34.8% for Aß40, 38, and 42, respectively). ANOVA results for differences among types of tubes was highly significant p = 0.005. Tukey post-hoc comparisons suggested that the Sarstedt 10mL SC Tube (15x92 RB PP GWB Str cat# 62.610.201) had the lowest mean loss across Aß species (-9.7) and differed significantly from all other tube types but one, even after adjustment for multiplicity. For tubing types a regression analysis with percent difference as the response, volume of CSF an explanatory variable, and tubing type as the factor of interest was performed with a quadratic term added to the model. Aß40, 38 and 42 were analyzed separately and for each analysis the quadratic term was significant (p < 0.05). For both Aß40 and 38 there was a significant difference due to tube type (p = 0.037) with Silastic having a lower response consistently across all CSF volumes. For Aß42 there was an interaction between volume and tubing type (p = 0.049) suggesting that for lower CSF volumes (under 6mL) Silastic is superior but for larger volumes Tygon is better. This study supports the use of specific collection/storage and tubing types when conducting CSF biomarker studies in order to reduce the loss Aß due to nonspecific binding.