Elecsys CSF AD immunoassays: Sample stability for a new pre-analytical protocol for fresh CSF.
Author(s): Manuilova E, Schrurs I, Rutz S, McIlwrick S, Goldhardt O, Sommer P, Grimmer T
Publication: Alzheimers Dement, 2025, Vol. 21, Page e70797
PubMed ID: 41104599 PubMed Review Paper? No
Purpose of Paper
The purpose of this paper was to compare levels of Amyloid beta 1–42 (Aβ42), tau phosphorylated at threonine-181 (p-tau181), and total tau (t-tau) in cerebrospinal fluid (CSF) stored at room temperature for up to 6-8 days, at 2-8°C for up to 13-15 days or at -25 to -15°C for up to 12-15 weeks with a single freeze-thaw cycle. Case-matched specimens from patients being evaluated for Alzheimer's disease were assigned to a single storage temperature experiment.
Conclusion of Paper
Levels of Aβ42, p-tau181, and t-tau decreased progressively with room temperature storage of CSF (slope= -0.791%, P<0.001; slope= -0.408%, P<0.001; and slope =-0.501%, P=0.005, respectively); however, all three were considered stable for 8 days as the confidence bound did not cross below 90% recovery until after the last timepoint. Levels of Aβ42, p-tau181, and t-tau were unaffected by CSF storage at 2-8°C for up to 15 days, with median, minimum, and maximum recoveries of each remaining within 93-105% of baseline. Levels of Aβ42, p-tau181, and t-tau were stable during CSF storage at -25 to -15°C for up to 8 weeks with a single freeze-thaw cycle, with very strong correlations (r>0.99, all) and low biases (<3%) observed between baseline and the 5-8 week timepoint (r>0.99, for all). While p-tau181 and t-tau remained stable when CSF was stored frozen for 12-15 weeks with a single freeze-thaw cycle, Aβ42 displayed a bias of -5%, resulting in levels of Aβ42 below 90% in approximately 30% of specimens. Nevertheless, levels of all three analytes remained very strongly correlated with baseline after 12-15 weeks (r>0.99) and slopes were close to 1 (0.992 for Aβ42, 0.971 for p-tau181, and 1.010 for t-tau). The authors recommend that CSF be stored at 15–25°C for ≤5 days, at 2–8°C for ≤15 days, and at -25°C to -15°C for ≤8 weeks.
Studies
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Study Purpose
The purpose of this study was to compare levels of Aβ42, p-tau181, and t-tau in CSF stored at room temperature for up to 6-8 days, at 2-8°C for up to 13-15 days or at -25 to -15°C for up to 12-15 weeks with a single freeze-thaw cycle. Five aliquots of CSF were collected by gravity drip lumbar puncture into lo-bind tubes from patients (≥ 50 years of age) being evaluated for Alzheimer’s disease. CSF specimens were stored at 15-25°C for up to 6 h before experimental storage at room temperature for 0, 1-3 or 6-8 days (specimens from 13 patients); storage at 2-8°C for 0, 1-3, 6-8 or 13-15 days (specimens from 14 patients); or storage at -25 to -15°C for 0, 5-8 or 12-15 weeks; frozen CSF was thawed for 30 min upright at 20-25°C and mixed on a roller mixer for 20 min (specimens from 42 patients). Levels of Aβ42, p-tau181, and t-tau biomarkers were measured using Elecsys CSF immunoassays. The percent recovery was calculated for each specimen and storage condition. For the short-term storage experiment, an OLS regression model was fitted, and when the slope was statistically significant (p < 0.05), the maximum allowable storage duration was calculated. For the medium-term stability experiment, acceptance was defined as a slope estimate within 1.00 ±0.07 and bias <7%.
Summary of Findings:
Levels of Aβ42, p-tau181, and t-tau decreased progressively with room temperature storage of CSF (slope= -0.791% P<0.001; slope= -0.408%, P<0.001; and slope =-0.501%, P=0.005, respectively); however, all three were considered stable for 8 days as the confidence bound did not cross below 90% recovery until after the last timepoint. Levels of Aβ42, p-tau181, and t-tau were unaffected by CSF storage at 2-8°C for up to 15 days, with median minimum and maximum recoveries of each remaining within 93-105% of baseline. Levels of Aβ42, p-tau181, and t-tau were stable during storage at -25 to -15°C for up to 8 weeks with a single freeze-thaw cycle, with very strong correlations (r>0.99, all) and low biases (<3%) observed between baseline and the 5-8 week timepoint (r>0.99, for all). While p-tau181 and t-tau remained stable when stored frozen for 12-15 weeks with a single freeze-thaw cycle, Aβ42 displayed a bias of -5%, resulting in levels of Aβ42 below 90% in approximately 30% of specimens. Nevertheless, levels of all three analytes remained very strongly correlated with baseline after 12-15 weeks (r>0.99) and slopes were close to 1 (0.992 for Aβ42, 0.971 for p-tau181, and 1.010 for t-tau). The authors recommend that CSF be stored at 15–25°C for ≤5 days, at 2–8°C for ≤15 days, and at -25°C to -15°C for ≤8 weeks.
Biospecimens
Preservative Types
- Frozen
- None (Fresh)
Diagnoses:
- Alzheimer's Disease
Platform:
Analyte Technology Platform Protein Immunoassay Peptide Immunoassay Pre-analytical Factors:
Classification Pre-analytical Factor Value(s) Storage Storage temperature Room temperature
2–8°C
-25 to -15°C
Storage Freeze/thaw cycling 0 cycles
1 cycle
Storage Storage duration 0 days
1-3 days
6-8 days
13-15 days
5-8 weeks
12-15 weeks