Pre-analytical stability of novel cerebrospinal fluid biomarkers.

Stability of the cerebrospinal fluid (CSF) composition under different pre-analytical conditions is relevant for the diagnostic potential of biomarkers. Our aim was to examine the pre-analytical stability of promising CSF biomarkers that are currently evaluated for their discriminative use in various neurological diseases. Pooled CSF was aliquoted and experimentally exposed to delayed storage: 0, 1, 2, 4, 24, 72, or 168 h at 4 °C or room temperature (RT), or 1-4 months at -20 °C; or up to 7 freeze/thaw (f/t) cycles, before final storage at -80 °C. Eleven CSF biomarkers were screened using immunoassays, liquid chromatography, or enzymatic methods. Levels of neurogranin (truncP75), chitinase-3-like protein (YKL-40), beta-site amyloid precursor protein cleaving enzyme 1 (BACE1), acetylcholinesterase (AChE) enzymatic activity, theobromine, secreted protein acidic and rich in cysteine-like 1 (SPARCL-1) and homovanillic acid (HVA) levels were not affected by the applied storage conditions. 3-Methoxy-4-hydroxyphenylglycol (MHPG) levels linearly and strongly decreased after 4 h at RT (-10%) or 24 h at 4 °C (-27%), and with 6% after every f/t cycle. 5-Methyltetrahydrofolate (5-MTHF) (-29% after 1 week at RT) and 5-hydroxyindoleacetic acid levels (5-HIAA) (-16% after 1 week at RT) were reduced and 3,4-dihydroxyphenylacetic acid (DOPAC) levels (+22% after 1 week at RT) increased, but only after >24 h at RT. Ten out of eleven potential CSF novel biomarkers showed very limited change under common storage and f/t conditions, suggesting that these CSF biomarkers can be trustfully tested under the pre-analytical conditions present across different cohorts.

Neurogranin and tau in cerebrospinal fluid and plasma of patients with acute ischemic stroke.

BACKGROUND: While neurogranin has no value as plasma biomarker for Alzheimer's disease, it may be a potential blood biomarker for traumatic brain injury. This evokes the question whether there are changes in neurogranin levels in blood in other conditions of brain injury, such as acute ischemic stroke (AIS). METHODS: We therefore explored neurogranin in paired cerebrospinal fluid (CSF)/plasma samples of AIS patients (n = 50) from a well-described prospective study. In parallel, we investigated another neuronal protein, i.e. tau, which has already been suggested as potential AIS biomarker in CSF and blood. ELISA as well as Single Molecule Array (Simoa) technology were used for the biochemical analyses. Statistical analyses included Shapiro-Wilk testing, Mann-Whitney analyses and Pearson's correlation analysis. RESULTS: In contrast to tau, of which high levels in both CSF and plasma were related to stroke characteristics like severity and long-term outcome, plasma neurogranin levels were only correlated with infarct volume. Likewise, CSF neurogranin levels were significantly higher in patients with an infarct volume > 5 mL than in patients with smaller infarct volumes. Finally, neurogranin and tau were significantly correlated in CSF, whereas a weaker relationship was observed in plasma. CONCLUSIONS: These findings indicate that although plasma and CSF neurogranin may reflect the volume of acute cerebral ischemia, this synaptic protein is less likely to be a potential AIS biomarker. Levels of tau correlated with severity and outcome of stroke in both plasma and CSF, in the present study as well as previous reports, confirming the potential of tau as an AIS biomarker.