Cerebrospinal fluid (CSF) analysis is a group of laboratory tests that measure chemicals in the fluid that surrounds and protects the brain and spinal cord. The tests may look for proteins, sugar (glucose), and other substances. A sample of CSF is needed. A lumbar puncture, also called a spinal tap, is the most common way to collect this sample. Less common ways to take a fluid sample include: 1  Cisternal puncture.  Removal of CSF from a tube that is already in the CSF, such as a shunt, ventricular drain, or pain pump.