Elecsys CSF AD immunoassays: Sample stability for a new pre‐analytical protocol for fresh CSF

INTRODUCTION Amyloid beta 1–42 (Aβ42), tau phosphorylated at threonine‐181 (p‐tau181), and total tau (t‐tau) are cerebrospinal fluid (CSF) biomarkers for Alzheimer's disease diagnosis. METHODS We prospectively examined storage time, temperature, and freeze/thaw effects on Aβ42, p‐tau181, and t‐tau stability in fresh CSF samples using Elecsys ® CSF immunoassays. RESULTS All three biomarkers were stable at 2–8°C for ≤15 days, and −25°C to −15°C for ≤8 weeks, and after one freeze/thaw cycle. p‐Tau181 and t‐tau were also stable at 15–25°C for ≤8 days and at −25°C to −15°C for 12–15 weeks. Aβ42 recovery declined slightly after storage at 15–25°C for ≤8 days and −25°C to −15°C for 12–15 weeks, and one freeze/thaw cycle. DISCUSSION For optimal immunoassay performance, it is recommended to store CSF samples at 15–25°C for ≤5 days, 2–8°C for ≤15 days, and −25°C to −15°C for ≤8 weeks. Highlights Cerebrospinal fluid (CSF) biomarkers aid in Alzheimer's disease diagnosis. Fresh CSF stored at 15–25°C for ≤5 days is optimal for Elecsys CSF immunoassays. Fresh CSF stored at 2–8°C for ≤15 days is optimal for Elecsys CSF immunoassays. Fresh CSF stored at −25°C to −15°C for ≤8 weeks is optimal for Elecsys CSF immunoassays.