• Normal CSF may contain up to 5 WBCs per mm3 in adults
  • Blood contaminating CSF in the setting of haemorrhage or traumatic tap can disrupting the white cell count
  • The ratio of WBC to RBC in blood is roughly 1:750
  • It is suggested to correct the white cell count by subtracting 1–2 WBC per 1,000 counted RBC in CSF