Clear, colourless fluid that fills spaces within and around the central nervous system.
Note: CSF originates from plasma by a biological ultrafiltration process. Specimens are obtained by a lumbar puncture (i.e. a spinal tap).
Source:
PAC, 2018, 90, 1121. 'Terminology of bioanalytical methods (IUPAC Recommendations 2018)' on page 1124 (https://doi.org/10.1515/pac-2016-1120)