![]() TBM is typically a subacute disease with symptoms that may persist for weeks before diagnosis. Results should normally be available within 1 hour of sample receipt for the acute unit, or within 24 hours for samples received from outside the acute units. Tuberculous meningitis (TBM) is the most common form of central nervous system tuberculosis (TB) and has very high morbidity and mortality. The test can be ordered as an urgent request. The in-lab turnaround time is less than 24 hours. The assays are run throughout the day and night. The date and time of the current lumbar puncture.The time and date of the onset of current symptoms/event.Date of any previous lumbar puncture (if within the last month).Sample tube: 2mLfluoride-oxalate tube (grey top).Sample tube: Plain Universal container (tubes containing gel or anticoagulant are not suitable for analysis of CSF protein).Samples from CGH are sent directly to GRH Pathology from the ward or from CGH Pathology if delivered there.Results on bloodstained samples will be unreliable.1mL of CSF is approximately equal to 25 drops from the Luer connector of the needle.If other investigations required please check CSF Sample Requirements for further details. Glucose levels are usually normal in viral infections of the CNS.Whilst not diagnostic, low glucose levels, as compared to plasma levels, are seen in bacterial meningitis, cryptococcal meningitis, malignant involvement of the meninges and sarcoidosis.These levels may be as low as 20 to 30 mg/dL (1.1 to 1.7 mmol/L). There may be a 2–4 hour lag in the CSF level when compared to the blood level. CSF glucose levels in the absence of meningitis are > 75 of the serum value measured at the same time. Glucose levels in CSF normally reflect the levels seen in the blood.When CSF protein levels are low it can indicate rapid CSF production.Moderate or pronounced elevation may be caused by acute bacterial meningitis, tuberculous meningitis, spinal cord tumour, cerebral haemorrhage, Guillain-Barre syndrome.Mild protein elevation may be caused by viral meningitis, neurosyphilis, subdural haematoma, cerebral thrombosis, brain tumour, multiple sclerosis (rarely >1.00 g/L).CSF protein concentration may rise due to 2 factors: either an increased permeability of the blood brain barrier allowing more protein and higher molecular weight proteins to enter the CSF or proteins may be synthesised within the cerebrospinal canal by inflammatory or other invading cells.Most of the protein that is normally present is albumin. The spinal fluid normally contains very little protein since serum proteins are large molecules that do not cross the blood-brain barrier.
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