Cerebrospinal Fluid Analysis

Cerebrospinal fluid (CSF) is an invaluable diagnostic window to the central nervous system (CNS). Commonly performed tests on CSF include protein and glucose levels, cell counts and differential, microscopic examination, and culture. CSF protein concentration is one of the most sensitive indicators of pathology within the CNS. As a general rule, CSF glucose is about two thirds of the serum glucose measured during the preceding two to four hours in a normal adult. Glucose in the CSF of neonates varies much more than in adults, and the CSF-to-serum ratio is generally higher than in adults. The WBC count seen in normal adult CSF is comprised of approximately 70 percent lymphocytes and 30 percent monocytes. Occasionally, a solitary eosinophil or neutrophil will be seen in normal CSF. Several neutrophils in a neonatal patient’s CSF is not unusual.

Elevated CSF protein is seen in infections, intracranial hemorrhages, multiple sclerosis, Guillain Barré syndrome, malignancies, some endocrine abnormalities, certain medication use, and a variety of inflammatory conditions. Protein concentration is falsely elevated by the presence of RBCs in a traumatic tap situation. Low CSF protein levels can occur in conditions such as repeated lumbar puncture or a chronic leak, in which CSF is lost at a higher than normal rate. Low CSF protein levels also are seen in some children between the ages of six months and two years, in acute water intoxication, and in a minority of patients with idiopathic intracranial hypertension. CSF protein levels do not fall in hypoproteinaemia. CNS infections can cause lowered CSF glucose levels, although glucose levels are usually normal in viral infections. Normal glucose levels do not rule out infection, because up to 50 percent of patients who have bacterial meningitis will have normal CSF glucose levels. Gram stain is positive in 60 to 80 percent of untreated cases of bacterial meningitis and in 40 to 60 percent of partially treated cases.

2 ml CSF Room Temperature

State serum glucose level. Avoid blood contamination. Increased WBC/CSF requires a di"erential count

Colour: Colourless Appearance: Clear Glucose, CSF: 50 - 80 mg/dL Protein, CSF: 15 - 60 mg/dL Chloride, CSF: 120-130 mmol/L RBC, CSF: < 1x10^6/L WBC, CSF: Adults: < 5x10^6/L Neonates: < 30x10^6/L