To be used in the investigation of suspected subarachnoid haemorrhage (SAH) when an initial CT scan is negative and clinical suspicion of SAH remains. This is the only indication for CSF xanthochromia analysis.
Bleeding into the CSF following SAH will increase the concentration of oxyhaemoglobin due to its release from lysed red blood cells. This oxyhaemoglobin is converted to bilirubin in a time-dependant manner. A small amount of oxyhaemoglobin may also be converted to methaemoglobin (rarely detected). Bilirubin is formed from in vivo in the CSF following a bleed, therefore is presence is suggestive of SAH. CSF bilirubin may also be increased due to increased serum bilirubin or total protein. Analysis may therefore require measurement if serum bilirubin and total protein in addition to CSF xanthochromia analysis to enable appropriate interpretation of results.
A net bilirubin absorbance of less than 0.007 absorbance units (AU) does not support SAH. Interpretative comments are provided with each result.
SAH is a type of stroke, most often caused by the rupture of an intracranial aneurysm.
Lumbar puncture should be performed no earlier than 12 hours after the suspected event for CSF xanthochromia to enable the formation of bilirubin from any free oxyhaemoglobin present in the CSF due to SAH.
White topped, universal containers should be used for CSF specimen collection. At least 200uL (0.2mL) is required for CSF xanthochromia analysis and specimens must be protected from light at all times once collected. Specimens should not be transported via the pneumatic tube system. Normal practice is to use the final specimen collected (usually specimen number 4) for CSF xanthochromia analysis.
A paired serum sample should also be sent for measurement of serum bilirubin and total protein if required to aid interpretation.
Within 2 hours.