Impact of frequent cerebrospinal fluid sampling on Aβ levels: systematic approach to elucidate influencing factors

BACKGROUND: Cerebrospinal fluid (CSF) amyloid-beta (Aβ) peptides are predictive biomarkers for Alzheimer’s disease and are proposed as pharmacodynamic markers for amyloid-lowering therapies. However, frequent sampling results in fluctuating CSF Aβ levels that have a tendency to increase compared with baseline. The impact of sampling frequency, volume, catheterization procedure, and ibuprofen pretreatment on CSF Aβ levels using continuous sampling over 36 h was assessed. METHODS: In this open-label biomarker study, healthy participants (n = 18; either sex, age 55 − 85 years) were randomized into one of three cohorts (n = 6/cohort; high-frequency sampling). In all cohorts except cohort 2 (sampling started 6 h post catheterization), sampling through lumbar catheterization started immediately post catheterization. Cohort 3 received ibuprofen (800 mg) before catheterization. Following interim data review, an additional cohort 4 (n = 6) with an optimized sampling scheme (low-frequency and lower volume) was included. CSF Aβ(1–37), Aβ(1–38), Aβ(1–40), and Aβ(1–42) levels were analyzed. RESULTS: Increases and fluctuations in mean CSF Aβ levels occurred in cohorts 1–3 at times of high-frequency sampling. Some outliers were observed (cohorts 2 and 3) with an extreme pronunciation of this effect. Cohort 4 demonstrated minimal fluctuation of CSF Aβ both on a group and an individual level. Intersubject variability in CSF Aβ profiles over time was observed in all cohorts. CONCLUSIONS: CSF Aβ level fluctuation upon catheterization primarily depends on the sampling frequency and volume, but not on the catheterization procedure or inflammatory reaction. An optimized low-frequency sampling protocol minimizes or eliminates fluctuation of CSF Aβ levels, which will improve the capability of accurately measuring the pharmacodynamic read-out for amyloid-lowering therapies. TRIAL REGISTRATION: ClinicalTrials.gov NCT01436188. Registered 15 September 2011. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13195-016-0184-z) contains supplementary material, which is available to authorized users.