A CSF sample is obtained by a physician usually via lumbar puncture in the L3-L4 region. A sterile technique is always used to reduce the risk of infection. Care must be taken to avoid injury to neural tissue.
A syringe is used to remove 6–20 mL of spinal fluid in an adult. However, the opening pressure is first measured and if it is elevated greater than 200 mm, no more than 1–2 mL of CSF would be withdrawn. Less fluid is removed in babies and small children. The CSF sample is divided into 3–4 tubes, with 2–4 mL in each tube.
Glass tubes should not be used due to cell adhesion, which may affect the cell count or differential. The tubes are numbered in the order in which the CSF is obtained.
