VALIDATION OF CSF TUBES FOR USE ON THE LUMIPULSE ® G PLATFORM: IMPACT ON Aβ1-42

The β-amyloid(1–42) (Aβ1–42) peptide present in the cerebrospinal fluid (CSF) is known to adsorb to plastics, with Aβ1–42 recoveries depending on the type of plastic. The consensus today is that polypropylene tubes should be used for CSF collection and storage. However, it has been shown that even between different polypropylene tubes, Aβ1–42 recovery still varies. The new Lumipulse G β-Amyloid 1–42 assay (Fujirebio) was designed for the fully automated analysis of CSF Aβ1–42 on the LUMIPULSE G Systems. These instruments allow for the placement of commonly used CSF tubes on the sample carrousel/rack, in addition to the option of using an auto-analyzer cup that is made of polystyrene and commonly used with fully automated instruments. The aim of the current study was to compare the auto-analyzer cup with three different CSF storage tubes in terms of Aβ1–42 recovery. The first experiment compared the Aβ1–42 concentration in 17 CSF samples between direct measurement from storage tubes vs. transfer from storage tube to auto-analyzer cup. The second experiment compared the concentrations of the same 17 CSF samples calculated on calibration curves made in the auto-analyzer cups and the three different tubes. In a third experiment, the Aβ1–42 recovery in three CSF pools was determined after four consecutive transfers in both the auto-analyzer cup and the storage tubes. The mean Aβ1–42 recoveries in the first experiment were 101%, 104% and 104% for transfer to the auto-analyzer cup from tube no. 1, 2 and 3, respectively. There was no impact on Aβ1–42 concentration of the tube in which the calibration curve was measured. Consecutive transfers of CSF into the same type of tube gave rise to a maximal drop in Aβ1–42 recovery to 89% for the auto-analyzer cup and 59%, 70% and 69% for the respective CSF storage tubes. The results show that (i) the Lumipulse G β-Amyloid 1–42 concentration is not significantly impacted by a transfer to the auto-analyzer cup, showing that the auto-analyzer cup can be used reliably for the quantitative measurement of CSF Aβ1–42, and (ii) confirm the heterogeneity in results obtained in different polypropylene storage tubes.