Spinal tap should be performed at least 12hrs following suspected SAH.
Send to laboratory Urgently - must be spun within 1hr.
Tube 4 is the preferred tube.
Cover sample with foil to protect from light.
Please note - if the sample is received after being unprotected from light this can lead to a decrease in bilirubin and a false negative result for Xanthochromia. Please interpret with this in mind and in the context of other tests and clinical history.
Reference: Foroughi M, Parikh D, Wassell J, Hatfield R. Influence of light and time on bilirubin degradation in CSF spectrophotometry for subarachnoid haemorrhage. Br J Neurosurg. 2010 Aug;24(4):401-4”