Cerebrospinal fluid (CSF)

Suspected bacterial meningitis (infection within the sub-arachnoid space between the pia mater and arachnoid) should be confirmed by CSF culture unless LP is contraindicated. Please indicate where high risk organisms are implicated (such as TB).
Please number containers clearly (1,2,3 etc), tube 3 should be labelled for MC&S and will be used for the cell count. A high WBC count along with a positive Gram stain supports a diagnosis of bacterial meningitis, but a negative Gram stain does not exclude meningitis. Where subarachnoid bleed is suspected please send 3 tubes (numbered 1,2 & 3) so that comparison can be made between a traumatic tap and SAH. Microbiology will perform microscopy, isolation, identification and susceptibility of any organism likely to be pathogenic. Microscopy results are available within 4 hours of receipt of sample, negative culture results will be issued at 48 hrs, positive cultures 2-3 days.
Where possible, send separate tubes for separate tests as specimens may be processed for a wide range of tests in different departments including virology, cryptococcal Ag, AAFB, where clinically indicated. Likewise any specimens for cytopathological examination should be sent separately as MC&S will render specimens unusable for this. If Xanthachromia is required, send a tube to Reference Chemistry, this should be covered to avoid light damage.
Clinical details: 
Meningitis, encephalitis, sub-arachnoid haemorrhage, meningoencephalitis
Synonyms or keywords: 
CSF, SAH, Meningitis, encephalitis, sub-arachnoid haemorrhage, meningoencephalitis
Sample type and Volume required: 
Cerebrospinal fluid. Please send 3 consecutive samples numbered 1 to 3 collected in sterile universal containers. (Ideally a minimum of 2ml in each tube)
Call in advance: 
Any CSF sample received by CSR by 17.00 is treated as urgent, but please Bleep out of hours (17.00-9.00) on bleep number 1802
Turnaround time: 
Cell count and Gram stain same day (within 4 hrs), Culture result 2 - 3 days. Significant Gram stain and culture results are telephoned to the ward by Microbiology Clinical staff.
Special sample instructions: 

Use of sterile technique for performing lumbar puncture and decanting sample into sterile universal containers. Ensure sufficient CSF is collected for the tests requested. If in doubt, contact the medical microbiologist.

Storage and transport: 
Please place labelled universal containing CSF samples in a sealed transport bag and send to Central Specimen Reception (CSR). Remember to send fluoride sample and Universal sample to Chemistry for Glucose and Protein estimation
Infection Sciences Department at St Thomas' Hospital
020 7188 8008
St Thomas' Hospital
North Wing - 5th Floor
Westminster Bridge Road
London SE1 7EH
Core opening hours: Monday-Friday 0900-1730

For clinical advice or interpretation of results, please contact the laboratory in the first instance.

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Last updated: 27/11/2017