Turnaround times
The quoted turnaround time is from sample receipt in the laboratory, to results authorisation in the Laboratory Information Management system. The times do not include transport of specimen to the laboratory or the administrative process to print and post/email reports. Service users must allow for transport and reporting time when ordering tests.
Clinical background:
The glucose level in CSF is proportional to the blood glucose level and corresponds to 60-70% of the concentration in blood. Therefore, normal CSF glucose levels lie between 2.2 and 4.4 mmol/L. Hypoglycorrhachia (low CSF glucose levels) can be used in the investigation of CNS infections, inflammatory conditions, subarachnoid hemorrhage, hypoglycemia (low blood sugar), impaired glucose transport, increased CNS glycolytic activity and metastatic carcinoma. It is useful in distinguishing causes of meningitis as more than 50% of patients with bacterial meningitis have decreased CSF glucose levels while patients with viral meningitis usually have normal CSF glucose levels.
There is no pathologic process that directly leads to hyperglycorrhachia (high CSF glucose levels) and therefore, high CSF glucose levels have no specific diagnostic importance.
Specimen container paediatric:
Fluoride oxalate tube
Specimen container adult:
Fluoride oxalate tube
Minimum volume paediatric:
0.5 mL CSF
Minimum volume adult:
0.5 mL CSF
Sample stability :
5 hours at 15 to 25°C,
3 days at 4 to 8°C,
>1 month at -20°C
Interpretation:
Provided that CSF for glucose estimation has been mixed with fluoride a low glucose concentration occurs in:
1. Infection
CSF glucose is normally metabolised only by cerebral cells. If many leucocytes and bacteria are present these also utilise the sugar and abnormally low levels are obtained. If obvious pus is present the estimation of CSF glucose adds nothing to diagnostic precision. It is most useful when the CSF is clear and tuberculous meningitis is suspected, although levels are not as low in this condition as in pyrogenic meningitis.
2. Hypoglycaemia
CSF glucose concentration parallels that of blood, although there is a lag before changes in blood glucose are reflected in the CSF. In the presence of hypoglycaemia (which may cause coma) CSF glucose levels may be low although there is no primary cerebral abnormality. In case of doubt both blood and CSF concentrations should be measured. In hyperglycaemia CSF glucose levels will be high.
Low CSF glucose and decreased CSF glucose to blood glucose ratio may also be seen in GLUT1 deficiency syndrome.
Reference ranges:
Up to 18 years: 3.33 – 4.44 mmo
l/L18 years and over: 2.22 – 3.89 mmol/L