A protocol for the management of canine cerebrospinal fluid for the proteomic assessment of putative biomarkers

Cerebrospinal fluid (CSF) is a potential source for disease-specific biomarkers that may assist in the staging and determining the prognosis of neurodegenerative conditions in animals. However, the validity of such putative biomarkers may be influenced by pre-analytical variables, including the procedures adopted to collect and store the CSF. This study assessed the effect of three handling practices on the stability of a panel of CSF proteins: clusterin (also known as apolipoprotein J), haptoglobin, cystatin C, and transthyretin (TTR). The three handling procedures for canine CSF were mimicked in the laboratory as follows: (1) storage in a refrigerator overnight (4 °C for 18 h); (2) carrying a sample in the pocket of a clinician (37 °C for 4 h); and (3) mailing a sample to a remote laboratory for analysis (room temp for 48 h). The impact of these three scenarios on the concentrations of the selected proteins was assessed using Western blotting and compared to an aliquot of CSF that had been kept frozen.The level of clusterin was significantly reduced following 48 h at room temperature (P < 0.05), while the concentration of the dimeric form of TTR increased following this handling procedure and also when held at 37 °C for 4 h. A reducing agent prevented this increase at 37 °C. In conclusion, exposing CSF samples to various environmental conditions can significantly alter their protein content, a factor that must be considered in studies assessing potential biomarkers in canine CSF.