This test is performed to attempt to identify those patients who have had a subarachnoid haemorrhage (SAH) but in whom the CT scan is negative. Analysis of the CSF may detect bilirubin and this finding is consistent with a bleed into the CSF.
The formation of bilirubin after haemorrhage is a time-dependant process and bilirubin may not be detectable soon after the event (e.g. onset of severe headache). On current evidence it is recommended that CSF is not sampled until at least 12 hours after a suspected event.
Collection of samples
CSF sample collection packs are available from the Pathology Department which include all the required specimen containers, full instructions on the collection procedure and a brown envelope to protect the zanthochromia sample from light.
Label 4 white-topped universal containers with:
- the patient’s name,
- NHS number
- date of birth
- time that CSF was obtained
- the sequence order of sampling (e.g. sample no 3)
Collect the universal containers numbered 1- 3 (aim for a total of 2 mL) and send with the blue request form to Microbiology, informing them by telephone that the samples will be arriving.
Collect the 4th universal container containing a minimum of 1 ml CSF (approx 20 drops from a Luer connector on a needle). Protect this sample from the light, and send with gold-top blood sample to Clinical Biochemistry with a green request form with the request for CSF xanthochromia, CSF protein and serum bilirubin and protein. Obvious blood stained samples may not be analysed as interpretation will be difficult under these circumstances.
The samples are reported as CSF Net bilirubin absorbance and CSF Oxyhaemoglobin with interpretation.